This column generally takes a sceptical view of financial novelties and gimmicks. So my antennae have twitched in recent days at frequent mentions of Spacs, or ‘Special Purpose Acquisition Companies’, which are the latest plaything of Wall Street and could be about to go large over here. Also known as a ‘blank cheque’ company, a Spac is a stockmarket-listed cash shell that raises money with a view to merging with a real — usually hi-tech, often relatively early-stage — business seeking a fast route to listed status.