One of the first things they discovered – thanks to the restaurant’s manager as she showed them round – was the foundation stone plaque, on the side of the building, for the whole Gorbitz development, unveiled just the previous year.

The manager also showed them a mural linked to the origin of the restaurant’s name. It was nothing to do with historic horse-drawn police vans – the mural showed a scene from the novel Der grüne Heinrich by the Swiss author, Gottfried Keller. The woman was about to outline the novel’s plot when Müller felt she had to intervene.

‘We’re not here for a tour of your establishment, citizen. We’re simply seeking information about one of your regular customers, Bodo Achterberg.’

‘Of course,’ said the woman, nervously pulling at the sleeves of her overalls. ‘You did say as much. Sorry, we’re just very proud of the new restaurant and it’s not often we get a visit from the police. I think the best place to start is the skittle alley in the basement – Bodo spent most of his spare time there.’

From what they’d heard of the man so far, and his prodigious drinking habit, Müller couldn’t imagine him having a steady enough hand for skittles, but she and Tilsner dutifully followed the woman down the concrete steps to the basement.

Even now – in the middle of the day – virtually every skittle lane was busy, but most of the customers were clearly pensioners. The manageress approached one man, and brought him over to speak to the two detectives.

The man introduced himself as Albert Planck and claimed to have known Bodo well.

‘Bodo was a wreck I’m afraid, but he still didn’t deserve what happened to him.’

‘And what,’ asked Tilsner, acidly, ‘have you heard happened to him?’

‘Well . . .’ The man hesitated, as though he knew he was repeating rumours. ‘You know . . . buried in concrete and all that. Can’t have been pleasant.’

‘There’s been no confirmation of Herr Achterberg’s fate, dead or otherwise,’ said Müller. ‘So please don’t go repeating tittle-tattle.’

‘Sorry,’ said the man. ‘It’s just, as you can imagine, it’s all anyone’s talking about round here.’ A loud cheer rang out, followed by sustained applause. ‘Someone must have scored a ringer. Let’s move over there by the bar. It’ll be quieter.’

Once they were seated on a circular red leatherette bench seat around a beige melamine table, Müller started to question him in more detail about Bodo.

‘You say he was a “wreck”. What do you mean by that?’