If the New York Stock Exchange winds up buying Euronext one major question will remain: what will NYSE chief executive John Thain do about the London Stock Exchange?

Insiders say Mr Thain still very much wants a deal with his London counterparts. But that might be tough to swing if he is still trying to close a complex Euronext merger. Now some Wall Street analysts and exchange shareholders say there is but one logical answer: do both at once.