They found a parking bay, and Grant dropped a couple of coins into the machine, peeling back the ticket and sticking it to the inside of his windscreen.

‘Half an hour long enough?’ he asked.

She shrugged. ‘Depends what we find.’

They walked past the Last Drop pub, named for the fact that criminals had swung from Grassmarket’s scaffold at one time in the city’s history. Victoria Street was a steep curve back up to George IV Bridge, lined with bars and gift shops. On the far side of the street, pubs and clubs seemed to predominate. One place doubled as a Cuban bar and restaurant.

‘What do you reckon?’ Siobhan asked.

‘Not too many statues, I wouldn’t have thought, unless there’s one of Castro.’

They walked the length of the street, then doubled back. Three restaurants this side, along with a cheesemonger and a shop selling nothing but brushes and string. Pierre Victoire was the first stop. Peering through the window, Siobhan could see that it was a fairly empty space with little in the way of decoration. They went in anyway, not bothering to introduce themselves. Ten seconds later they were back on the pavement.

‘One down, two to go,’ Grant said. He didn’t sound hopeful.

Next was a place called the Grain Store, through a doorway and up a flight of stairs. The place was being readied for lunchtime trade. There were no statues.

As they descended to the street, Siobhan repeated the clue. ‘“This queen dines well before the bust.”’ She shook her head slowly. ‘Maybe we’ve got it wrong.’

‘Then the only thing we can do is send another e-mail, appeal to Quizmaster for help.’

‘I don’t think he’s the type.’

Grant shrugged. ‘Next stop, can we at least have a coffee? I skipped breakfast this morning.’

Siobhan tutted. ‘What would your mum say?’

‘She’d say I slept in. Then I’d tell her it’s because I was up half the night trying to solve this bloody puzzle.’ He paused. ‘And that someone had promised me breakfast would be on them …’

Restaurant Bleu was their final call. It promised ‘world cuisine’ but had a traditional feel as they walked through the door: old varnished wood, the small window doing little to illuminate the cramped interior. Siobhan looked around, but there wasn’t so much as a vase of flowers.

She turned to Grant, who pointed towards a winding staircase. ‘There’s an upstairs.’

‘Can I help?’ the assistant said.

‘In a minute,’ Grant assured her. He followed Siobhan up the stairs. One small room led to another. As Siobhan entered this second chamber, she gave a sigh. Grant, following her, thought the worst. Then he heard her say, ‘Bingo,’ in the same instant as he saw the bust. It was Queen Victoria, two and a half feet high, in black marble.

‘Bloody hell,’ he said, grinning. ‘We cracked it!’