Artemis was in the mood to demonstrate his genius. This was a mood in which he frequently found himself. And as satisfying as these demonstrations were for the fourteen-year-old Irish boy, they could be intensely irritating for anyone on the receiving end.

'Firstly, it is hardly likely that there is a sniper gunning for me,' he said. 'I have liquidated eighty per cent of my illegal ventures and spread the capital across an extremely lucrative portfolio.

Secondly, any audio-tech trying to eavesdrop on us may as well pack up and go home as the third button on your jacket is emitting a Solinium pulse that whites out any surveillance tape, human or fairy.'

Butler glanced at a passing couple, who were bewitched by Spain and young love. The man had a camcorder slung round his neck. Butler fingered his third button guiltily.

'We may have ruined a few honeymoon videos,' he noted.

Artemis shrugged. 'A small price to pay for my privacy.'

'Was there a third point?' asked Butler innocently.

'Yes,' said Artemis, a touch testily. Still no sign of the individual he was expecting. 'I was about to say that if there is a gunman on one of these buildings, it's that one directly to the rear. So you should stay behind me.'

Butler was the best bodyguard in the business, and even he couldn't be a hundred per cent sure which rooftop a potential gunman would be on.

'Go on. Tell me how you know. I know you're dying to.'

'Very well, since you ask. No sniper would position himself on the rooftop of Casa Mila, directly across the street, because it is open to the public and so his access and escape would probably be recorded.'

'His or her,' corrected Butler. 'Most metal men are women these days.'

'His or her,' amended Artemis. 'The two buildings on the right are somewhat screened by foliage, so why handicap yourself?'

'Very good. Go on.'