You're entitled to ask why you should be interested in a comedian you've never heard of who died 60-odd years ago. Bob Hope called Sid Field "probably the best comedian of them all". For Tony Hancock, Field was inspirational and David Suchet tells a good story with actorly flourishes. Tragically, scarcely a fragment of Field in action survives. Yet we get a glimmer of how Field created the character-based sketch comedy that's become the norm in British comedy. He also pioneered camp - "the original mince," observes Julian Clary, tartly.

Sky doesn't make many dramas, but when they do they make them well. Going Postal is Sky's latest Terry Pratchett adaptation, a big budget extravaganza in two parts, filmed upon elaborate sets and exquisitely costumed, that lovingly recreates Pratchett's weird and wonderful alternative universe of Discworld.

Richard Coyle stars as confidence trickster and irrepressible charmer Moist Von Lipwig, spared from the gallows to perform the equally lethal task of reviving the Ankh-Morpork postal service. Postmaster General is an office with a one hundred per-cent mortality rate, with several fingers of suspicion pointing firmly in the direction of ruthless entrepreneur Reacher Gilt (David Suchet) who will stop at nothing to impose his Clacks communication system upon the populace.

Frantic, funny, romantic, silly and frequently touching, Going Postal delivers in many, many ways.

Nearly always it's the quiet ones that surprise you with their anger. Terry Pratchett's delightful series of surreal Discworld novels have long bewitched readers. Pratchett novels have always acted as gentle satires of our world, but Going Postal, the latest of his novels to be filmed by Sky was, by Pratchett's standards at least, monumentally angry.

Porcine bankers, the celebration of corporations, the moral vacuity of the concept of victimless crime and, er, the incorrect use of apostrophes, were all fed into the novel that was the source for this Sky adaptation. The anger was mollified for family viewing - but only slightly.

David Suchet, almost unrecognisable as a villain who resembled an ageing, heavy metal star, played Reacher Gilt - the rapacious owner of Clacks, a network of semaphore towers which are Discworld's take on the internet.

This was a man who had taken advantage of a banking crisis to move in and steal Clacks from its inventor. Gilt was enraged when the patrician Lord Vetinari (Charles Dance) pardoned conman Moist von Lipwig (Richard Coyle) on the understanding he revive the Discworld's postal service to provide some competition to Clacks.

Part of the glory of this fabulous chunk of entertainment was that Sky eschewed CGI in favour of lavish sets, constructed with lashings of sparkling invention. Going Postal looked amazing. Luckily, everything else about the production was dazzling too.

Coyle was roguish but sympathetic, and Andrew Sachs, as his assistant, bumbled along like a cross between his Fawlty Towers duffer Manuel and the original grandfather from Only Fools And Horses. Claire Foy, as Adora Dearhart, smouldered convincingly.

Terry Pratchett's Going Postal, a two-part special from Sky1 which concludes tonight, had a pretty distinguished cast too. Presumably the thesps in question were attracted not just by the money, but also by the always-welcome chance to don some eccentric facial hair and shout a lot. Then again, they could even have been attracted by the script - because the programme is enormous and imaginative fun.

Needless to say, with its origins in a Pratchett novel, the imagination does tend to the bonkers. Richard Coyle plays Moist von Lipwig, a con man rescued from hanging by the mysterious Lord Vetinari (Charles Dance, salt-and-pepper beard and moustache). He was then given the job of reviving the Ankh-Morpork Post Office, much to the fury of the man who runs the Discworld equivalent of the internet, Reacher Gilt (David Suchet, Fu-Manchu moustache, beard and eye-patch). Moist's allies include the elderly junior postmaster Mr Groat (Andrew Sachs, huge moustache) and the toothsome Adora Belle Dearheart (Claire Foy, no facial hair but obviously enjoying putting Little Dorrit behind her by smouldering sexily and generally carrying either a cigarette or a riding crop).

With these - and plenty more - elements in place, last night's episode rattled along nicely, easily passing the key test for all programmes that seek to create another world: we gradually stopped noticing how mad that world was. By the end, in fact, it seemed perfectly logical that a seven-foot clay robot should have persuaded Moist to confess that he'd been responsible for the forged cabbage bonds which ruined Adora's family - while back at the Post Office a young man obsessed with pin-manufacture was attacked by a flying monster.

Sky may not have the resources to churn out top home-grown drama on a routine basis, but when it does decide to throw its weight behind a production, as it's done for this latest Terry Pratchett Discworld adventure, then it certainly does it in style.

Shot in HD, and with a fabulous British cast that includes David Suchet, Richard Coyle, Charles Dance, Claire Foy, Andrew Sachs, Steve Pemberton and Tamsin Greig, this Bank Holiday two-parter (concluding at the same time tomorrow) is a typically outlandish Pratchett tale about a lifelong con man who's given one last chance to avert the death sentence. The deal? He must take on the seemingly cursed task of trying to rescue Discworld's Post Office, under threat from their equivalent of the internet.

Sky's third venture into the cult fantasy world of Terry Pratchett (after Hogfather and The Colour of Magic), Going Postal again does justice to the author's peculiar vision. The weirdness of Discworld is appropriately captured in a tale of love and redemption which blends satire, humour and drama. It tells of a con artist, Moist von Lipwig (Richard Coyle), forced to atone for his crimes by taking the cursed role of postmaster at the dilapidated Ankh-Morpork's post office. The job puts him in the firing line of Reacher Gilt (David Suchet), who runs a rival delivery service, but also leads to an encounter with Adora Belle Dearheart (Claire Foy). Concludes tomorrow.

Going Postal: David Suchet on Reacher Gilt

David Suchet gives us an exclusive sneak peak at what it's like to play the villianous Reacher Gilt and how Terry Pratchett has helped him get to grips with such a dastardly character.