The New York Stock Exchange suffered a setback yesterday when its second-largest investor, Caldwell Asset Management, warned the board not to mount a bid for the LSE.

At this time it’s not known what effect this prohibition might have on any offer being prepared, nor on whether Caldwell intends the warning to be a deal-breaker.

If the NYSE pulls out before it has even declared itself, it will leave the way clear for Nasdaq to tie up a deal with Clara Furse. We expect it to have to pay around £12 ($20.88) per share to clinch it.

And with Euronext and Deutsche Borse occupied with creating a super-borse for the Eurozone, the Anglo-American courting couple could carry on their dalliance in relative peace.

But will NYSE comply with the warning? It would be a soggy response to an exceptional window of opportunity. Faint heart never won fair maiden. Clara would not be impressed.