Things to do:

Merseyside’s Second World War history is bloody, dramatic and, in many ways, crucial to the bigger picture: and here is the nerve centre of it all. Western Approaches HQ was the most important suite of rooms in the UK at the time.

Western Approaches, aka Derby House, aka Liverpool War Museum, comprises the subterranean operations rooms for the UK’s combined maritime operations during WWII. As such, it’s essentially where the Battle of the Atlantic was mapped out and planned, while British operations to the west of the British Isles and Ireland were monitored and directed.

The home for these operations moved to Liverpool in 1941, and Derby House – party of Exchange Flags – was kitted out with three-foot concrete walls and a seven-foot concrete ceiling. Closed into 1945 it was stripped out and most of the space converted to offices. Luckily the central reinforced core was deemed too expensive to demolish, and the rooms were restored to their original glory by the Walton Group some years ago.

At the centre of the tour, which still contains a significant amount of rooms and corridors, lies the Main Operation Room – an enormous map room of the kind seen in any WWII dramas set in Whitehall and the like. At the centre is a huge map of the western approaches, where the movements of Atlantic shipping was plotted and the battle of the Atlantic was won. It’s hugely impressive, and it’s easy to forget the real world outside, sealed in the wartime vaults. A voiceover tells the story of the military personnel who worked there, with the ambient noise of the map room also present.

There are endless rooms of authentic ancient equipment, junction boxes, switchboards, bunkbeds and telephones. A hotline to the War Cabinet, which would have been attended at all times by an armed guard, stands in a telephone box in one room.

Happily, there’s little to take you out of the moment. There are few, if any, modern details. No sounds are heard. There is no natural light. It seems all the more remarkable that the rooms are still there; a little part of England where World War II seems to be very real and very now.

• Western Approaches is open to the public in Summer months (1 March – 31 October) between 10.30-4.30pm every day except Fridays and Sundays.