I have travelled from France to march on Hurst Castle, fortified since the 1540s to keep us French out, and I am finding it as hard to reach the fort as my ancestors did. Unless you arrive by sea, you can only get to Hurst by walking along a 5km spit of shingle. The elements and history seem to be against me.
The southerly wind is so strong I can lean on it as if it were a wall. Swept to my left with each step, I must zigzag, tacking my way to the castle, feet deep in slippery pebbles. My hair flies up like kite-string and sea air sprinkles my skin with salt. The light makes me squint. The sea is in a state of insurrection. Waves roll towards the shore, then rear like horses, before suddenly crashing on to the steep gravel slope.
I think of my countrymen who thought, tried, and failed to land here in gale-force winds. I think of my distant relative Robert Surcouf, a famous privateer from St Malo, whose statue on the city's ramparts points a vengeful finger in the direction of England. With a movement of the arm, a fierce look and an engaging smile, he always seems to say, "Come with me! Together, we'll conquer Britain!"
Hurst Castle is the highlight of my 7km walk around Keyhaven on the Hampshire coast. As I approach the end of the spit, rock pipits show the way in through the original drawbridge. Used by the British army until 1957, the fort's various quarters point to its continuous use through the centuries. Conceived by Henry VIII to protect a key strategic position - the western entrance to the Solent, passage to the commercial port of Southampton and the naval base at Portsmouth - it became the most powerful defence establishment on England's south coast. Modernised during the Napoleonic wars and again in the 1860s and 1870s, with two massive wings, it was equipped with the latest weaponry to keep invaders at bay.
Until 1914, of course, Britain had one arch-enemy. In the shell store of the castle's east wing, a quote from a letter by Lord Palmerston to Gladstone in 1859 makes very clear the spirit that presided over Hurst's constant reinforcement: "We have on the other side of the Channel a people who, say what they may, hate us as a nation from the bottom of their hearts and would make any sacrifice to inflict a deep humiliation upon England."
What do you do when you fear your neighbour is out to get you? You build thicker and thicker walls and store up ever greater quantities of guns and powder. In the castle's Victorian wings, shell stores, powder rooms and cartridge hoists greet you at every corner. Two austere bathrooms and a bread oven remind me that the enemies of France were not only made of iron. However, the size of the cannons, still in their firing positions, would make anybody, friend or foe, shudder. Twelve men were needed to operate these 39-tonne monsters; each shell weighs over 360kg and could be fired some 5km.
Walking back in time, I leave Victoria's age for Henry's world. Hurst's Tudor tower, circular within, is a beauty. Charles I was imprisoned here in 1648, and I walk on stones that he paced nervously for 19 long days just before his execution. I don't know why but I feel more at ease with the English civil war than with Victoria's relentless and bourgeois reign. I have always preferred times of unrest.
On the tower's roof, haunted by the memory of heavy artillery positioned in every embrasure, the view over Hampshire and the Isle of Wight is superb. I can see two little white and red boats ferrying visitors back and forth from the castle to the mainland and, in the distance, the Gun Inn.
I came by foot; I'll leave by sea. The ferry boat glides slowly through rows of moored yachts. The boats' names - Extreme, Vibrant, Dame - sound familiar. We could be in a little fishing port in Brittany, couldn't we?
Just beyond the quiet salt marsh, I join Englishmen and women peacefully drinking their pints of ale in the dark corners of the Gun Inn. In the distance the wild southerly wind whips the union flag above Hurst Castle into a reassuring blur of blue, white and red. The enemy France is forgotten, at least for now.
• Agnès Poirier walked route 2461 (Henry VIII's sea fort), an "easy" 7km. For step-by-step instructions and local attractions, see here
