The four capitals each have fortifications with their own story: Cardiff Castle haunted by the Marquess of Bute who restored it in the 19th century; The Tower of London the scene of thousands of executions; Edinburgh with its one oclock gun and Stone of Destiny; Belfasts which nearly ruined the Donegalls when it was rebuilt in 1870.
Castles are a painless way to teach kids history: Dover Castle makes a great stop off when crossing the channel, a fortified introduction to British history from Roman times to WWII.
These days, though, many of Britains castles show some imagination beyond retelling history. Alnwick in Northumberland Hogwarts in the Harry Potter films amuses guests with medieval games, dressing up, and falconry. Ludlow Castle, a magnificent reminder of how unsettled the marches once were, is the venue for plays and concerts during that towns festival. Traquair Castle, the oldest inhabited house in Scotland, revived its brewhouse some time ago and produces fantastic beers. Bamburgh north of Newcastle has an aviation museum - and if the kids are bored the beach is only yards away.
But perhaps it is just the look of the things that fascinates us. Framlingham Castle in Suffolk with its 12 towers, a rival for the chateaux of the Loire; Scotlands romantic Eilean Donan Castle near Skye proving that small can be utterly beautiful; and the marvellously symmetrical Beaumaris on Anglesey.
A castle makes a great focus for a day out, and leaves memories for a lifetime.