Merrill Lynch is to be the sole bookrunner of a $500m (€456m) convertible bond from Carnival Corporation, despite being joint corporate broker to the US cruise operator with UBS Warburg.

Both banks were advisors on its takeover of UK competitor P&O Princess Cruises. The convertible bond comes the day after Carnival shares began trading under its dual-listed company structure, the first to involve a UK and a US company.