Dr Pratt considered the board then took the chalk stick from his fellow operative. ‘Without limit?’ he said. ‘Okay, so we just keep on adding connections to either end of this chain of thought?’

Dr Pratt ringed ‘Nightclubs’, then ‘Opticians’ Newspapers’; the two discoveries either end of O’Singh’s flow chart.

‘Yes!’ exclaimed O’Singh, as if something had been explained to him and the penny dropped.

‘Well that is a bit limiting isn’t it?’ huffed Dr Pratt. ‘I mean, what for example are we to discover further from ‘Nightclubs’?’

‘Dayclubs? Could there be anything in dayclubs?’ returned O’Singh, racking his brain. ‘Dawnclubs perhaps, or duskclubs, crepuscular-clubs? – you know, clubs with very restricted opening hours?’

‘Not sure. Alternatively, what can we go on to discover from Opticians’ Newspapers?’

‘I am sure something will make itself known,’ ventured O’Singh, hopefully.

‘My feeling is that this is going to take quite some time,’ sighed Dr Pratt, stepping over to O’Singh’s countdown calendar to discovering everything on the wall. ‘You do know that it can take quite a while to discover everything?’ he said, rapping the calendar lightly with his knuckles.

‘Well now you put it like that…’

‘We are somewhat limited,’ insisted Dr Pratt. ‘Not quite, I’m afraid, the quantum leap in our knowledge you had hoped for.’

‘Not quite. Perhaps something a little more modest than a quantum leap? – like a “quantum shuffle”?’