Poppa had taken an especial shine to Lady Mary, Sir Cuthbert’s elegant wife, who had designed the gardens herself. ‘You should see them, little Kathleen.’ He waved his arms expansively, nearly unseating her from his lap, as he described the sequence of separate areas: the Round Garden made from the foundations of a Martello tower, the lily pond in the formal Italian garden, and the kitchen garden the size of a cricket pitch with a beautiful ornate glasshouse they called the lemonry. ‘Though whatever you’d want with all those sour old fruits beats me,’ he’d muttered.

The most extraordinary feature of the gardens was the way they’d used artificial rocks to build grottoes and tunnels, and even a winding pathway along the very edge of the cliff, with little seats and viewpoints. ‘Just like a fairy story,’ he said with a wistful sigh. ‘Never seen anything like it, not around these parts.’

Everyone had heard tell of glittering nights at the Manor in the old days, when the winding lanes along the peninsula would be clogged with vanload after vanload of food and drink and Lady Mary ordered so many flowers that the ferry had to make three journeys. After dark the place was lit with coloured lights, and orchestras could be heard late into the evening, even from the Felixstowe side.

For her fourteenth birthday Ma had given her a book about an American millionaire who hosted the most glamorous parties in the world, and she’d instantly pictured it set at Bawdsey Manor in that mirrored ballroom and on the terraces from where, Poppa said, you could see the lights of Harwich eight miles away. That the hero failed to find happiness despite his wealth never troubled Kath’s visions. She wanted to be the girl he’d fallen in love with and even, for a few weeks, tried to insist that her friends call her Daisy. But it never seemed to stick, and she soon gave up.

Today, as she and Joan stood looking across the river, all the glamour of the place seemed to have evaporated. The fairy-tale castle looked forlorn, its entrance festooned with officious signs: KEEP OUT. NO ENTRY TO UNAUTHORISED PERSONS. REPORT TO GUARDHOUSE. Behind the house stood a tall mast, like the Eiffel Tower, she was sure had never been there before. All along the wall surrounding the estate were slung coils of shiny barbed wire. Spanning the gateway was a new barrier with a uniformed guard standing beside it. As they watched, vans waited in a queue while he laboriously checked their papers before allowing them to pass.

‘Crikey, look at that. They really don’t want anyone in there, do they? I wonder why?’

‘My dad said they’d sold the place to the Air Ministry, and there’s some kind of top secret stuff going on,’ Joan said.

‘I hope that don’t stop us using the beach.’ The red-tinted sands bordering the river, south-facing and sheltered by the low bluff on which the Manor sat, were a favourite place for picnics. You could swim at high tide, and if you searched carefully enough you might find sharks’ teeth and other fossils left over from the Ice Age. Crossing the river by ferry was the only way to get there from Felixstowe if you wanted to avoid a twenty-mile road journey up to Ipswich and back, along the winding road from Woodbridge and out along the northern shore of the River Deben.