Now that we have spent some time together in a locked-down country, we all know what it is like to be stuck inside a sitcom. What we are feeling now is what the likes of Basil and Sybil Fawlty, Mainwaring and Wilson, Hancock and Sid, Albert and Harold Steptoe, Del Boy and Rodney Trotter, Hacker and Sir Humphrey and Father Ted and Dougal, have been feeling throughout their entire comic existence.

Pascal once famously remarked: 'All of humanity's problems stem from man's inability to sit quietly in a room alone.' Pascal would have hated sitcoms.

Sitcoms are all about trapped relationships, where there is nowhere to run to, nowhere to hide, and in those episodes where they trap those relationships within an even more cruelly confined space, they take you straight down deep into their lonely soul. These are the ultimate lockdown episodes, the shows about nothing but isolation.

'To make a sitcom work,' the writer Barry Took once told me, 'you have to nail the characters' feet to the floor.' So now that our own feet have been nailed to the floor, we can re-view some of these sitcoms, and some of their best episodes, with greater empathy and insight than we've ever done before.

Take the classic episode from Hancock's Half Hour, Sunday Afternoon At Home. Set inside 23 Railway Cuttings, East Cheam, during the late 1950s, when every single Sunday felt like a lockdown, it captures perfectly the creeping feeling of tedium that comes when the clocks seem to slow almost to a stop and life just lumps itself down at your feet in a hopeless heap. It is like a Samuel Beckett play reimagined by Alan Bennett.

The quartet inside the house play four recognisable lockdown types. Sid is the sad-faced fatalist: 'There's nothing we can do about it,' he sighs, as he stares at the newspaper and tries to lose himself in the hopelessly implausible horoscopes of Arnold the Gypsy and the gallstone-zapping claims of some unnamed pseudo-scientist. Griselda, on the other hand, is the dogged optimist: 'Ooh, look,' she exclaims excitedly, 'it's started raining!' Bill, meanwhile, is quietly reaping the benefits from already having a locked-down brain: 'Let's play "Beat Your Neighbours Out of Doors,"' he proposes at one point, before admitting that he has no idea how to play it.

Hancock himself, however, represents, in this special context, the sitcom character for whom the spell has been broken: he suddenly realises what he really is, a trapped character, and, like a fly in a fly bottle, he is searching desperately for an escape.
'Oh, I do hate Sundays,' he moans. 'I'll be glad when it's over. Drives me up the wall, just sitting here looking at you lot'.

It is not that Hancock is against indolence. Far from it. He simply resents having indolence imposed upon him by outside forces. 'I think I'll go to bed,' he mutters, in a vain attempt to take control of the situation. 'You've only been up an hour!' he is reminded cruelly.

Time would normally take him away from all of this, but, in his locked-down world, even time appears to have abandoned him. 'What's the time?' he asks. 'Two o'clock,' he is told. 'Is that all?' he exclaims. He sighs, stares into space, sighs, and then tries again: 'Are you sure it's only two o'clock?' No, he is told: 'It's one minute past two now'. 'One minute past two?' he replies. 'Doesn't the time drag!'

He is not standing for this. He is not sitting for this. He flatly refuses to embrace the boredom.

Thus fighting Canute-like against the waves of ennui that keep on washing in, he first tries an interpretative strategy:

Still desperate to drive the dullness away, Hancock then tries to recruit the others for an impromptu session of name that tune:

Still refusing to give up, he attempts to start a game of Monopoly:

Finally, he resorts to the classic locked-in tactic of looking out: he starts spying on the neighbours:

Now he is desperate for any distraction, but the fruit bowl is empty, the record player is broken, the key to the piano lid is lost and the television set is kaput. 'Oh, I give up!' he exclaims. 'I'm not coming downstairs next Sunday. I'll have one of me pills on Saturday night and wake up on Monday!'

The torture is not over yet, however, because his next-door neighbour, a heat-seeking missile of a bore-meister called Clark, has now turned up.

Hancock tries to distance himself through rudeness - 'It's raining, you know!' declares Clark perkily. 'Oh, so that's what's making the roads wet!' snaps Hancock - but this unbidden interloper, already self-isolating from his cold-ridden wife, Rosita, is utterly oblivious of how unwelcome his presence actually is ('I'm all right for an hour or two...').

'The real reason I came in,' he reveals to the horror of Hancock, 'is because, well, it gets a bit boring, sitting in there on a Sunday afternoon by yerself. There's nothing much to do, is there?'

Even after insisting on performing his entire mind-numbingly tiresome repertoire of animal impressions ('Moooooo!' 'Ruff! Ruff! Ruff!' 'Moooooooo!' 'Ruff! Ruff! Ruff!' - 'That's a cow being worried by a sheepdog'), and following an unsubtle nudge from an exasperated Hancock ('I'm sorry you can't stop for tea but we haven't enough fish paste to go round'), the neighbour still can't take the hint: 'I don't mind. You just go ahead. I'll just sit here'.

Hours later, with everyone else except Hancock now fast asleep, he is still going:

Finally, after seven hours and six hundred animal sounds, Clark is finally off: 'Did you realise it's nearly twelve o'clock?' he asks a heavy-lidded Hancock. 'Is that all?' groans Tony. 'I thought it was at least Tuesday!'

The clock then duly strikes midnight, everyone else wakes up, and at long last this particular lockdown is over:

Today, now that every day feels like Sunday, there is something rather therapeutic about this episode: it reminds us that although, like then, the streets outside are eerily empty, the shops are shut and there is nowhere to go, at least we now have the internet, YouTube, 24-hour TV, DVD box sets, streaming services, Spotify, Skype, smart phones, fast food home delivery services and even 4-ply quilted toilet rolls - so we don't have to focus on the wallpaper, hum half-forgotten tunes, or try to dig out old board games, and, thank goodness, your next-door neighbour isn't allowed to come round for tea.

Sunday Afternoon At Home, however, is a depiction of lockdown that still seems quite benign in its tetchy restlessness when compared with the blood-boiling tension on show in an episode of Steptoe And Son entitled Divided We Stand. Here is another, darker, phase of lockdown, where the people trapped together have grown so heartily sick of the sight of each other that both of them seek their own private lockdown from the lockdown.

Set in the Seventies, inside the Steptoes' cramped old home-cum-storage facility at Oil Drum Lane, Shepherd's Bush, Divided We Stand explores what happens when familial ties tighten too much for anyone to endure. Here is father Albert, selfish, scheming and cynical, and here is son Harold, dreamy, desperate and delusional, stuck together in a confined and cluttered space, when sanity starts to snap.

It starts with a typical element of lockdown fatigue: a sense of exasperation about having to endure such an over-familiar environment.

The chronically restless Harold, desperate to feel that he is at least moving on aesthetically if not physically, proposes redecorating their shared hovel of a home in the most bourgeois style that he can imagine ('Wedgewood blue on the ceiling...Etruscan red for the woodwork...'), only to be rebuffed, yet again, by his obstinately proletarian father ('Bleedin' awful - it'll look like a Peruvian brothel!'). 'At least let us agree the colour scheme of the bog,' barks Harold, but Albert brusquely refuses to play the game, beyond suggesting that they simply use all the free wallpaper samples: 'Bung all the bits up!'

They've reached their usual impasse, except this time, for Harold, it's happened one time too often:

Unable to agree on anything except their incompatibility (HAROLD: 'Not to put too fine a point upon it, Dad, your very presence tends to impinge upon my aesthetic moments, my little bits of relaxation.' ALBERT: 'In other words: I get on your tits.'), these two desperate people try to find freedom within their mutual prison by partitioning the house in two.

Suddenly, Harold is up and active, sawing wood, hammering nails, erecting a long and winding dividing wall, and installing a coin-operated turnstile for entering and exiting no man's land: the stairs and the kitchen. 'I'm free!' Harold tells himself excitedly as he surveys his small but precious personal territory. 'I'm on me own at last! I've complete privacy for the first time in my life! Oh, the peace! The quiet!'

It does indeed seem, for a fleeting moment, that the new arrangement is working. Harold is now able to indulge himself in his dream of a more civilised existence, donning a fancy smoking jacket and decorating his table with an assortment of vintage silver and crystal, while Albert is left to wallow in the squalor, eating greasy chicken wings with his hands and slurping builder's tea from a battered old enamel mug.

It does not take long, however, before it becomes evident that even this drastic measure has failed to bring any real and lasting relief. Each new little bit of freedom has brought with it a new little bit of frustration.

Each doorway is now too narrow; the hot and cold taps are separated on the sink; the salt and pepper set is divided on the dining table; and, perhaps most infuriating of all in each man's locked-down little world, there is no way of achieving consensus as to who watches what on the now split-screened TV set:

Things go from bad to worse until, after a fire breaks out in the night, and the rescue services are delayed from responding ('Even the bleedin' firemen had to put pennies in the turnstiles!'), the two men are dragged kicking and screaming back to face their inescapable familial fate. Now stuck together again side by side, this time locked-down in the same hospital ward, in neighbouring beds, they are still arguing, still resenting each other's presence, and still with their feet nailed to the floor.

If that particular episode seems, in our current context, a little too dispiriting for our fragile temperaments, then our third and last example should provide quite a few precious crumbs of comfort.

This lesson comes from an episode of Dad's Army entitled Asleep In The Deep. From what is arguably the definitive 'locked-down' sitcom, seeing as it is set in state-run wartime Britain (rather than just a particular house or even a provincial prison), this is probably its quintessential locked-down episode.

It opens up in the usual way, with the diverse members of the platoon stuck together in the confined space of little Walmington-on-Sea, niggling each other with their class and cultural differences as they labour to defend their land:

Their situation is about to become even more claustrophobic, however, because two of their comrades, Walker and Godfrey, have been trapped in an underground room at the local pumping station, which has just been hit by a bomb. Once the rest of them, in an effort to stage a rescue, have ended up trapped in precisely the same place, along with the despised ARP Warden Hodges, the lockdown is complete.

What we now witness is a kind of comic microcosm of a whole nation suddenly shut away behind closed doors. All human life, and all human moods, are confined here, either to fall further and further apart or else come closer and closer together to forge a united front.

This is us. This is where we are. This is how we cope.

Mainwaring is the self-appointed leader and the most dourly-dutiful of cheer-uppers ('If there's any encouraging to be done, I'll do it!'); Wilson is the cautious realist ('Do you really think that's wise, sir?'); Jones is the always bayonet-ready action man ('You've got to be ready for the old upward thrust, sir!'); Pike is the playful child mercifully unware of what is really going on ('Uncle Arthur, would you like some hundreds and thousands?'); Walker (who these days, of course, would be beavering away busily on eBay, selling hand sanitisers and face masks at vastly inflated prices) is the irreverent joker ('The stopcock's on the pipe, cock!'); Godfrey is the mild-mannered pragmatist ('Don't you think it might be a good idea if we didn't talk so much, and then we might save the air a bit?'); Hodges (who today would be finger-wagging about social distancing while furtively stockpiling pasta pots and paracetamol) is the archetypal jobsworth ('Now wait a minute, this has got nothing to do with me!'); while Frazer, of course, is a Celtic vampire of the human spirit, sucking out positivity so fast that his colleagues' legs are left pale and shaking in his wake ('We're doomed...DOOMED!').

The locked-down platoon is helped initially by the fact that, as they have an established chain of command, the man at the top can at least use his powers to try to maintain morale:

Mainwaring's first emergency measure is that peculiarly British response to adversity, the awkward-sounding sing-song:

This works moderately well, in the circumstances, until one of the water pipes springs a leak, first soaking Pike and then gradually filling up the rest of the tiny room. Driven to take refuge up on Godfrey's bunk bed (except for Pike, who is left down on the floor to serve as a human water level gauge), the mood soon sinks to one of deep dark-watered gloom.

From that point on, Mainwaring's leadership eerily anticipates today's unnerving political Micawberism:

With Mainwaring now blatantly bereft of ideas, however, the anti-social element in the community comes sadly to the fore in the form of the fabulously misanthropic Hodges, scowling in the isolation of his floating metal bath:

This is the kind of miserable locked-down moment for which the greatest fatalists were born, and Frazer is thus now in his element: 'The water...The water's getting higher and higher...We're entombed!' he cries, as the water continues to flow in, the platoon tries not to panic, and Pike gets even wetter.

Warming to his task like a sad-eyed scientific advisor, Frazer growls on unbidden: 'I'm minded of the time I was a wee bonnie laddie on the lone Isle of Barra. A submarine got sunk in Castlebay. And seven brave men were trapped in it. The water got higher and higher and higher...until it got up to their necks...and then...Hmmm...Terrible way to die...'

Mercifully, before he can depress everyone else any further, the platoon is free: Godfrey, of all people, has woken up and found a shadowy manhole that leads to freedom. This extra-special lockdown is over for them (at least for the moment), as, one hopes, it will soon be over for us.

That is one of the enduring charms of Dad's Army. Of all of Britain's sitcoms, it is the one whose trapped relationship remains the most pertinent to the broadest audience, because it is about the trapped relationship that we all happen to share, and, in contrast to the hopelessness of Hancock or the self-destructiveness of the Steptoes, it offers us a bit of hope.

Some of us are stuck in the middle right now with maybe a Mainwaring, or a Wilson, a Pike, a Jones, a Walker, a Godfrey, a Frazer or even a Hodges, or possibly some combination of these types, or perhaps even the whole lot of them. What we know, thanks to the show, is that, for all of their, and our, many foibles and flaws, we will get through this better together.

That is what we can learn, at this odd and unnerving moment, when we watch our classic sitcoms. We're peering through the window at the isolated, and, uniquely for now, they are peering back out at us. So we should laugh at ourselves as well as them, and take comfort from the fact that at least our own lockdown will only be temporary.