'Sure,' I said. Poppy was laughing at something the policeman told her. How could she find him so amusing?

'I put Werner in charge of the communications room security one night back in September 1978. There was a lot of signals traffic. The Baader-Meinhof gang had hijacked a Lufthansa Boeing, and Bonn was convinced they were flying it to Prague… You ask your wife about it, she'll remember that night. No one got a wink of sleep.'

He sipped some of his brandy. 'About three o'clock in the morning, a cipher clerk came in with an intercept from the Russian Army transmitter at Karlshorst. It was a message from the commanding general requesting that some military airfield in southwest Czechoslovakia be kept operational on a twenty-four-hour basis until further notice. I knew what that message referred to because of other signals I'd seen, and I knew it wasn't anything to do with the Baader-Meinhof people, so I put a hold on that message. My interception unit was the only one to file that signal that night, and I've checked that one through NATO.'

'I'm not sure what you're getting at, Frank,' I said.

'That damned message went back through Karlshorst with "intercepted traffic" warnings on it. Werner was the only person who knew about it.'

'Not the only person, Frank. What about the cipher clerk, the operator, the clerk who filed the signal after you'd stopped it, your secretary, your assistant… lots of people.'

Artfully, Frank steered the conversation another way. 'So you were talking to dear old Werner last night. Where did this reunion take place – Anhalter station?'

The surprise showed on my face.

Frank said, 'Come along, Bernard. You used that old military identification card I let you have, and you were too damned idle to hand it back when it expired. You know those bogus cards have numbers that ensure we get a phone call when one turns up in a police report. I okayed it, of course. I guessed it was you. Who else would be in Leuschner's cafe at that time of night except drug pushers, pimps, whores and vagabonds, and that incurable romantic Bernard Samson?'

Joe Brady, the American 'from Siemen's' drifted over to us. 'What kind of caper are you two hatching up?' he said.

'We were talking about Anhalter station,' said Frank.

Joe Brody sighed. 'Before the war, that was the centre of the universe. Even now old-time Berliners walk out there to look at that slab of broken masonry and fancy they can hear the trains.'

'Joe was here in '39 and '40,' said Frank. 'He saw Berlin when the Nazis were riding high.'

'And came back with the U S Army. And shall I tell you something else about Anhalter Bahnhof? When we got copies of Stalin's order to his Belorussian Front and his Ukraine Front for a converging attack that would take Berlin and end the war, the point at which those great armies would meet was specified as Anhalter Bahnhof.'

Frank nodded and said, 'Joe, tell Bernard what we did about that Karlshorst signal… the one about the airfield remaining open for the Russian commanding general. Do you remember?'

Joe Brody was a bright-eyed bald American who held his nose while he was thinking, like a man about to jump into deep water. 'What do you want to know, Mr Samson?'

Frank Harrington answered on my behalf. 'Tell him how we discovered who had divulged that interception.'

'You've got to realize that this wasn't a big deal,' Brody said slowly. 'But Frank thought it was important enough to suspend the clearance of everyone on duty that night until we got a lead on it.'

'We checked everyone who handled the message,' said Frank. 'I had nothing against Werner. I suspected the cipher clerk, as a matter of fact, but he came out clean.'

'Was Giles Trent handling signals traffic at that time?'

'Giles Trent? Yes, he was here then.'

'No, no,' said Brody. 'No chance you can pin this on Giles Trent. The way I understand it, he had no access to signals traffic.'

'Can you remember so well?' I said.

Brody's gold-rimmed glasses flashed as he turned his head to be sure he wasn't overheard. 'Frank gave me a free hand. He told me to dig as deep as I wanted. I guess Frank wanted me to go back to my people and tell them you Brits weren't about to paper over the cracks in the future.' Frank wet his lips and smiled to show he was still listening even if he had heard the story before. 'So I dug,' said Joe Brody. 'It was your guy Werner something…'

'Werner Volkmann,' I supplied.

'Volkmann. That's right!' said Brody. 'We eliminated the others, one by one. This other guy – Trent, Giles Trent – took a little extra time because London got sticky about letting us read his file. But he was in the clear.' He grabbed his nose again. 'Volkmann was the leak, believe me. I've done hundreds of these investigations.'

'And never made a mistake?' I asked.

'Not that kind of mistake,' said Brody. 'I don't go around ripping away a security clearance just to make myself feel six feet tall. This was Volkmann. Not Trent, nor any of the others – unless everyone was telling me lies. So you can tell your people in London the file is closed on that one.'

'Suppose I told you Trent is now an orange file?' I said.

'Holy cow!' said Brody without too much emotion. 'Is this going to become another one of those?'

'It looks as if it's nipped in the bud,' I said. 'But I would take a lot of convincing that Trent wasn't in on your problem too.'

'I know the feeling, young man,' said Brody. 'Research and investigation are no damn use if they don't support those prejudiced judgments we've already worked so hard on.'

'Anyone except Werner – that's it, isn't it?' said Frank.

'No!' I said too loudly. 'It's not that.'

'Bernard was at school with Werner,' Frank explained to Brody. 'Your loyalty does you credit, kid,' said Brody. 'Jesus, I know guys in your position who'd be trying to pin it on their wife.'

Frank Harrington laughed and so did Brody.

The next morning, I had breakfast with Lisl. We sat in the room she called her study. It had a tiny balcony that looked out on the traffic of Kantstrasse.

It was a wonderful room and I remembered it from the time I was small, and permitted inside when my father came to settle his monthly account. Apart from the walls covered with small framed photos, there were a thousand other wonders for a child's eye. There were small tables littered with ivory snuffboxes, a brass ashtray fashioned from a section of World War I shell-casing, the words a present from lemberg hammered into the brass, and Russian buttons soldered round its edge. There were two fans, open to reveal Japanese landscapes', a small china zeppelin with berlin-staaken on its side; opera glasses made of yellowing ivory; and a silver carriage clock that didn't work. Most dazzling of all to the small boy I once was, a Prussian medal awarded to Lisl's grandfather, a magnificent piece of military jewellery suitably mounted on faded red velvet in a silver frame which Lisl's maids kept gleaming bright.

Breakfast was set on a small table against the window, which was open enough to move the lace curtain but not enough to move the starched linen table cloth. Lisl was seated in the high dining chair from which she could get up without assistance. I arrived exactly on time; I knew that nothing dooms a meeting with a German more completely than tardiness. 'Mein Liebchen,' said Lisl. 'Give me a kiss. I can't jump up and down – it's this damned arthritis.'

I bent over and kissed her, careful to avoid the heavily applied rouge, powder and lipstick. I wondered how early she must have risen to have prepared her hair and makeup. 'Don't ever change it,' I said. 'Your glamorous room is still as enchanting as ever.'

She smiled. 'Nein, nein.' That ummistakable Berlin accent: ny-yen, ny-yen. I knew I was home when I heard it.