Amid all the clamour over a merger that would create the world’s largest tanker company, a few veteran finance experts scratched their heads over one element of the announcement.

Crude giants Euronav and Frontline were announcing their $4.5bn combination based on an agreed term sheet, not a signed contract or “definitive documentation” in the parlance of merger-and-acquisition specialists.

The question: why?

“I don’t think I can remember this ever happening with the possible exception of a case where the deal was about to leak [publicly],” said one source with a long career in ship finance.