By City A.M. TClarke, the London-headquartered firm which powered the world’s first electrically lit building – the Savoy Theatre – is to head into private hands. The £91m buyout of the building and electrical outfit, announced yesterday, came on another sorry day for the already bruised London Stock Exchange. First,retailer Superdry announced that it would delist as part of a rescue deal, then hedgies Sparta published an open letter to the bosses of FTSE 250 stalwart Wood Group telling them to leave London due to an underperforming share price. But the move of TClarke, which listed in London …