Horrible Histories is truly a phenomenon, the books now running to more than 70 titles, selling millions of copies in many languages, with a highly successful TV show, and of course worldwide theatre tours. Parents love it because it makes education fun, encourages children (especially boys) to read and to visit the theatre, learning while laughing. I hadn’t realised until this performance that Terry Deary’s background was in theatre education, so now it all makes sense.

Windsor Theatre is situated right in front of the castle, and in this Royal Wedding week, Barmy Britain opened appropriately with a fanfare, followed after only a few minutes by a Meghan Markle name check. The premise of the show is that Rex (Benedict Martin) must convince Roger (Pip Chamberlin), and the rest of us, that Britain has a long tradition of being barmy.

This is a short (70 minutes), sharp whistle stop tour from Roman Britain to the First World War, propelled by jokes (many about bottoms and poo naturally), songs, dancing, costume changes, and of course, historical facts. A Horrible Histories speciality is to make the misery of the past fun, but only sort of, because it is anything but glossed over; it’s more that much of it is so dreadful that you can only laugh in amazement that it really happened, and in relief that you’re not there. But they are also canny in their use of contemporary popular culture, so we have the Roman cookery competition “Manky Chef”, will.i.am Shakespeare, Dick Turpin in TOWIE, and a great In Da Club Restoration Rap from Charles II.

Rex and Roger were excellent hosts, clearly seasoned performers, acknowledging that the auditorium was not exactly full, but still getting an audience battle going between Saxons and Vikings singing about English place names. The pace never faltered, and the jokes, scene changes and musical numbers carried us briskly along, although there was still time for some entertaining ad-libbing while drinking water from the cholera infected Broad Street water pump - happy days in the nineteenth century.

“Things get worse in the twentieth century…” they said, and even I was momentarily duped into thinking that must be wrong, until Lord Sugar’s interrogation into what went wrong with The Apprentice General Haig’s task. For a few seconds there actually was stunned silence when he admitted to exactly how many men he lost at the Somme, followed by Sugar’s inevitable and deserved riposte.

So with Roger, and the audience, finally convinced that we really are Barmy Brits, it must be time for a sing along - or two: “Hooray for Horrible!”

Book Horrible Histories tickets through our trusted official partner Ticketmaster.