As Horrible Histories turns 15, executive producer Simon Welton fills us in on what it's like to make the show...

16th April 2024 marks 15 years since we started broadcasting Horrible Histories. We've now made an incredible 162 half hour episodes and are on our 11th series. It's a total joy to work on a show that is so loved by its audience - young and old.

It all starts with a group of historians researching new pieces of history for us to write sketches about; and we will also occasionally bring in experts in a specific field, depending on the topics we're covering.

Each sketch is different - some will take half a day to shoot (especially the songs), and some can literally be shot in 20 minutes. Similarly, editing some sketches can be much faster than others, especially if they have lots of different segments in them. Overall, it usually takes around 15 months from the point at which the researchers kick everything off by starting to look for history facts, up until we deliver our final complete episode to CBBC, to make the 15 episodes that usually make up a series.

We have a core cast of actors who are on set most days - whom viewers will recognise despite the various incredible costumes and make up! Then there are a further half a dozen or so actors and guests who join us for a couple of days, or even weeks, across the series.

We've also been fortunate to have been joined by several famous faces across the years, including Rowan Atkinson, Rob Delaney, Mel Giedroyc, Meera Syal, Rosie Jones, Rob Rinder, The League Of Gentlemen, Stephen Fry, Robert Webb, Dara O Briain and Fred Sirieix...

Richie Webb writes and creates the music for every song, and has done so from the very beginning. He sometimes also writes the lyrics, but mostly they are written by a variety of different writers across the series - whoever comes up with the best idea, really! We even have a claim to fame in that a Horrible Histories song was quoted in a Medieval History Tripos Exam at Cambridge University in 2019.

The cast will carefully rehearse their song vocals before they come in to record them, but also during the vocal recordings we'll try different ways of singing something which will be unexpectedly funny, and that'll make us chuckle. A lot. Probably too much. On set, when we shoot sketches, there are definitely some that give the cast the giggles more than others, and they tend to be the very silly ones. Often, those moments come when a cast member suddenly improvises something brilliant - a bit of magic that wasn't there on the page.

Our 15th birthday episode is centred around the Tower of London - a really unusual setting. We mostly shoot in stately homes or historical sites that we use regularly and know well, so it was a special day to shoot in such a famous place with so much history. The quarries that we sometimes shoot in can also be unusual in that they're often working locations, so we'll have modern excavators working not too far away from where we are staging ancient Egypt!

Some sketches are really difficult to film, for a variety of reasons. In a sketch in the NHS episode, we had a prop baby that need to be sick into an actor's face not only on cue, but also with sufficient force that it would be visible properly on camera, and that it would hit the actor in the face in a way that was funny. Any mistakes there and we would have lost time because we'd need to clean up the actor and their costume before we could start shooting again, so that was an oddly tense comedy moment...

Another sketch that comes to mind is in the Holidays episode, because we were shooting outside a stately home but we were right under the flightpath into Heathrow Airport, so trying to time our shots in between planes landing (for sound recording) - it was almost impossible!

So it's been a wild, amazing, very special 15 years - it's the most fun show to make, and we're looking forward to delivering more Horrible History in the years to come too...

Horrible Histories: Terrifying Tower of London is available on BBC iPlayer now and will be broadcast on CBBC on Friday 19th April at 5:30pm.