He slid across the sofa, his finger tracing the light blue line which went through the station. ‘Do you see?’ he said.

‘No,’ she said grimly. ‘So you’d better tell me.’

‘Go one stop north of King’s Cross.’

‘Highbury and Islington?’

‘And again.’

‘Finsbury Park … then Seven Sisters.’

‘Now backwards,’ he said. He was practically bouncing on the spot.

‘Don’t wet yourself,’ she said. Then she looked at the map again. ‘Seven Sisters … Finsbury Park … Highbury and Islington … King’s Cross.’ And saw it. The exact same sequence, but abbreviated. ‘Seven … Fins … High Is … King.’ She looked at Grant. He was nodding. ‘Well done you,’ she added, meaning it. Grant leaned over and gave her a hug, which she squirmed out of. Then he leaped from the sofa and clapped his hands together.

‘I couldn’t believe it myself,’ he said. ‘The way it just suddenly screamed at me. It’s the Victoria Line.’

She nodded, couldn’t think of anything to say. It was indeed a section of London Underground’s Victoria Line.

‘But what does it mean?’ she said at last.

He sat down again, leaning forward, elbows on knees. ‘That’s what we have to work out next.’

She slid across the sofa a little, making some space between them, then lifted her pad and read from it. ‘“This queen dines well before the bust.”’ She looked at him, but he just shrugged.

‘Could the answer be in London?’ she asked.

‘I don’t know,’ he said. ‘Buckingham Palace? Queen’s Park Rangers?’ He shrugged. ‘Could be London.’

‘All these Underground stops … what do they mean?’

‘They’re all on the Victoria Line,’ was all he could think to say. Then they stared at one another.

‘Queen Victoria,’ they said in unison.

Siobhan had a London guidebook, bought for a weekend away which she’d never taken. It took her a while to find it. Meantime Grant booted up the computer and did a search on the Internet.

‘Could be the name of a pub,’ he suggested. ‘Like in EastEnders.’

‘Yes,’ she said, busy reading. ‘Or the Victoria and Albert Museum.’

‘Not forgetting Victoria Station – also on the Victoria Line. There’s a coach station there too. Worst cafeteria in Britain.’

‘You’re speaking from experience?’

‘I bussed it down there a few weekends in my teens. Didn’t like it.’ He was scrolling down some text.

‘Didn’t like the bus or didn’t like London?’

‘Both, I suppose. “Bust” couldn’t mean a drug bust, could it?’

‘Maybe. Or some stock-market crash. There was one not that long back, wasn’t there? Black Monday?’

He nodded.

‘Still, more likely it’s a statue,’ she said. ‘Maybe of Queen Victoria, with a restaurant in front of it.’

They worked in silence for a while after that, until Siobhan’s eyes started to hurt and she got up to make more coffee.

‘Two sugars,’ Grant said.