Frau Rolf got up and began rummaging around in a writing desk, bringing out a pad and a ballpoint pen. ‘I’ll write you down her address. She’s in Pirna – Sonnenstein, on the edge of Pirna, actually. It’s a new-build development of very nice apartments. She was very lucky to get one as a single person.’

Sonnenstein. The name immediately made Arnie shiver, as it would any historian of the Second World War worth his salt. One of the main euthanasia centres – part of the Aktion T4 programme.

The woman wrote down the address and then handed it to Arnie. ‘Will you stay for a coffee at least?’ she asked.

‘Thank you,’ he said. ‘That would be lovely.’ It wouldn’t be, of course. Now he was here, he was eager to get away from the sense of decay and sadness that seemed to pervade the hotel. But for politeness’s sake, he knew he would have to at least drink her coffee. He just hoped it was drinkable – East Germany’s excuse for coffee, with its ersatz ingredients, often wasn’t. ‘Milk and one sugar, if that’s OK.’ The next half hour would probably be the equivalent of watching paint dry – but it was only half an hour lost from his life.

*

The housing estate at Sonnenstein looked exactly how Arnie had expected. Identical blocks of identical flats. Already in the UK, such developments were passé – although Arnie knew there were plenty of examples of similar, brutalist architecture in Britain too, including in his home city. The Orchard Park estate, with its twenty-plus storey high-rises, was considered one of the worst places to live in Hull – built in the 1960s as part of a slum clearance, offering post-war modernity, just as the East German flats offered private bathrooms, toilets and kitchens – things that were often lacking in the DDR’s older apartment blocks.

Here – unlike in Orchard Park – everything looked well cared for. Arnie could see four high-rises, but counting upwards he could tell they weren’t quite as high as the hated ones in Hull. The other big difference here would be the level of employment. Unemployment rates in the Hull estate stood at nearly 20 per cent. Here, everyone who wanted a job would have one. Either at the energy and gas turbine plant – housed in the very buildings where the Nazis had carried out their euthanasia programmes – or at the nearby Leupoldishain uranium mine. Given a choice, Arnie knew where he’d prefer to work, history notwithstanding.

He quickly located Lotti’s block, the one with the pharmacist’s at one corner on the ground floor, and then entered the building and climbed to the third floor in search of her apartment, number 315. Was it fair to simply turn up unannounced? Would she even welcome the visit? Perhaps the past was better left alone.