Imagine the delight of an emerging art graduate, weighed down with worries for his future and a hefty student debt, when Charles Saatchi descends on his degree show and buys the lot.

I’m sure visions of smart private views and reserved stickers and museum wall spaces all play across the excitable imagination. And to an extent there is cause. Saatchi has made careers. This is the ad-man turned art collector who created the markets that launched the Brit pack. He sent not only their prices but their cultural credibility soaring when he wangled a show for them at that most traditional repository of high aesthetics, The Royal Academy.

But James Howard would be wise to be more wary. There are problems. Mr Saatchi tends to spread his bets. For every new protégé who emerges blinking amid the flashbulbs of fame, several more will languish as mere bit-part players in an enormous collection that rarely sees the light of day. Saatchi has never matched his Brit Art success. His awkwardly titled “New Neurotic Realism” movement sank without trace. His “Triumph of Painting” exhibitions, for all that they incorporated some very good works, were attempts to catch up, more than pioneering shows.

Mr Saatchi is also known for periodically pruning his collection rather severely. When in the mid-1980s he disposed of his holdings of Sandro Chia, he allegedly destroyed the reputation of the Italian painter, who has never got it back.

Mr Saatchi is an aggressively successful dealer whose transactions can make or break markets.

But it is as important to know what he is selling as to find out what he buys.

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