English Heritage is the charity that administers over 400 of England’s historic sites, spread right across the country and across time, from prehistory to the middle of the 20th century. It is linked to, but separate from, Historic England (the public body that lists and oversees historic sites and the Blue Plaque scheme) and sometimes, confusingly, it shares responsibility for a place with the National Trust. Many sites are open access and free.

Below I’ve ranked my 20 favourites, based on decades of experience travelling the length and breadth of the country. All are open during the October half-term and either full- or part-time throughout the year, but always check before setting out.

20. Dover Castle Tunnels, Kent

This mighty fortress, crouched on the coast, facing down France since the 1180s, has all you want from a castle: a Roman lighthouse, a mighty keep, towering walls and two sets of tunnels. The Secret Wartime Tunnels run parallel to the coast and were visited by Churchill during the Second World War. The less familiar medieval siege tunnels, on the north side, were hastily begun under attack around 1216, when the French dauphin joined forces with the English barons against King John. A new exhibition, Dover Castle Under Siege, explains the attacks, and you can go through the Spur Tunnels for the first time. There’s also a new siege-themed playground.

Stay: Dover Castle has two brilliant billets: Peverell’s Tower (sleeps two) and the Sergeant Major’s House (sleeps six). Three nights from £560 and £705, respectively.