Swallow decided on a lie-in in the morning. The Bremen Hotel served breakfast from seven o’clock to half past eight, but he was well fed from Elena Pfaus’s dinner of the night before. So he luxuriated in his warm bed until after nine. Then he rose, washed, shaved and dressed.

It would be midday before Pfaus would have collated whatever intelligence there might be in the files on Stefan Werner. It might yield something that could offer a line of approach in his resumed questioning of Carmody at the Kriminalpolizei headquarters. So he decided he would defer that task until the afternoon and spend the morning sightseeing.

The day was sharp and dry, with the sky a clear blue canopy over the German capital. Hard snow was compacted where the pavements met the walls of the buildings. But the walkways were swept clear and well gritted, offering the pedestrian a better foothold. He took coffee, a bread roll with butter and some spicy sausage at a café close by the hotel, and set off towards the government quarter. The official buildings were not particularly remarkable and seemed rather austere and functional compared to London or Dublin. But Bismarck’s new parliament building, the Reichstag, still under construction, was already impressive.

Pfaus had told him how to find the Imperial Art Gallery, just a short walk from the Reichstag. Remarkably, and to his delight, they had guidebooks available at the entrance in several languages, including English. But the collections were a disappointment. Not surprisingly, the work of the German school predominated. He advanced through long galleries hung with gloomy portraits of princes, bishops and sour Teutonic ladies, sometimes with fat children by their side. But the Italian, French and English collections were quite limited. The Italian displays at Foulks’s national gallery in Dublin were far richer and more varied. Only the sense that he should not waste an opportunity that would be unlikely to come again kept him moving through the poorly lit rooms.

He was relieved when his watch told him it was almost noon and time to rendezvous with Pfaus. He was familiar with the streets now, and he walked briskly to the offices of the Kriminalpolizei.

Pfaus was waiting for him with the satisfied look of a man who has discovered something he believes to be significant.

‘Now, Joseph,’ he grinned, ‘you will be able to tell your superiors in Dublin of the efficiency of the policing system of Berlin, of Germany, indeed.’

He turned the cover on the green cardboard file that sat before him on his desk.