If you are anything like me, then probably, the word "Dover" conjures up images of White Cliffs, seagulls and maybe even Dame Vera Lynne and Blue Birds. Whilst I have seen 50% of these images in Dover in reality, the Blue Birds and Dame Vera have so far eluded me. If, like us, you are regular travellers to the continent via Dover, then you cannot have failed to have seen Dover Castle perched up high above the White Cliffs overlooking the town to the west and port to the due south.

…..never mind, join us then, if you will on a voyage of discovery of one of the worlds' longest lasting, and probably, this countries last fully functioning castle.

You arrive at Dover Castle, on foot or by car, up a steep approach road. The bridge entering the castle grounds is only the width of a car, so if you are worried that you are at the back of a long queue, do not be. It will only be the traffic light control delaying you.

This is very much a military castle, as apposed to any form of 'home', stately or otherwise. It has a very plain strategic purpose, overlooking the coast of France in the narrowest section of the whole English Channel known as the Straights of Dover. For centuries enemies have been observed from here, invaders repelled. You do not need to be a military historian to appreciate this place, there is plenty for everyone to see along the way and you will depart educated on some aspect of history that you did not expect to find here.

The main 'above ground' castle building is the massive four square keep built by King Henry II during the 1170's and 80s. From this, and the fortified embankments around it, the castle grew. This keep only ended its military service in1945. As originally designed, it housed grand state apartments, two chapels and a very deep drinking well.

In Medieval and Tudor Times the state rooms and apartments would have remained empty - the King and court travelled with all their own luggage and furniture - the furniture being sent on ahead of the royal party.

Carrying on up the spiral staircase you emerge onto the roof of the Keep, from which a truly magnificent panorama of Dover, the coastline, the Straits of Dover and, on a clear day, France can be enjoyed. There are few places in my experience sharing such a view!

Back at ground level, after all that climbing of steps you may well be feeling in need of refreshment or a toilet even. Both an excellent café (serving good quality, reasonably priced food) and good clean modern toilets are to be found in the 1750s Keep Yard Barracks buildings, which enclose the northwest corner of the Keep Yard.

Going down the steep path from the main Keep area beware - it can be slippery even when not wet - you pass on the edge of the car park now disused 1850s officers barracks before emerging onto a small grass plateau area. Here are to be found Admiralty Look Out and the Port War Signal Station.

Apart from the Nuclear Tunnels, "Dumpey Level" as you will see them referred to, the hospital was the last development here at Dover, dug in 1941, but not fitted out until the autumn of 1942. These tunnels are steel lined and far less spacious than Napoleonic Casemate Tunnels at the lower level. Unlike the older tunnels, these are laid out on a regular grid pattern with a well designed layout of reception areas, washrooms, toilets, food stores, kitchens and, of course, operation theatres.

The Casemate Tunnels are considerably older, dating from the late eighteenth century. England was at war with France, Dover Castle was bursting at the seams with troops, provisions and munitions. By 1797 the room had literally run out. Under the supervision of the Royal Engineers miners were employed to dig seven parallel tunnels - running inside the cliff 50ft below the cliff top. At the rear of the tunnels a connecting passageway was then dug, linking all seven together. The tunnels were fitted out with sanitation, fireplaces and a well. By 1803 the first troops were billeted here, at the height of the Napoleonic Wars over 2000 men were homed in these tunnels.

Prior to 1939, the tunnels had remained largely abandoned for over a century. Just before the outbreak of the Second World War they were hastily turned into bombproof headquarters for the Royal Navy's Dover Command. A year later, Admiral Ramsay masterminded Operation Dynamo, the evacuation of Dunkirk from an office, with windows overlooking the Straights of Dover.

What the visitor sees here today is a recreation of the 1940s tunnels in their wartime role. Communication equipment at the time was undergoing rapid development, although it was far less compact than today, lacking up much space. Direct phone lines lead from here to Downing Street, the Admiralty, War Office and, of course, the local gun batteries and airfields - Biggin Hill, Manton and Hawkinge. Not only can you see all the switchboard equipment, but also the plotting tables, wall map and charts that played the most vital role in the defence of our nation.