As diplomatic questions go, whether the Foreign Secretary should take his mistress with him on a diplomatic tour ranks as one of the trickier examples.
With the prospect of meeting the Clintons in Washington, there would have been the tricky business over the canapes of whether to mention the president's own alleged extra-marital affairs.
Downing Street tried to damp down media interest in "Cook's Tour" with his mistress by scotching suggestions that the Foreign Secretary would be taking his live-in lover, Gaynor Regan, with him when he went to the White House on Thursday and Ottawa on Friday.
However, they could not rule out the possibility that Ms Regan, who is now sharing the Foreign Secretary's official residence, Carlton House Terrace, would accompany Robin Cook on next week's tour of China and Hong Kong.
Officials scratched their heads and said they could not find a precedent. There were occasions, said a Downing Street source, when a partner should accompany a minister abroad, particularly if there were social events to host.
Mr Cook announced on Sunday that he planned to marry Mrs Regan after he had divorced his wife, Margaret.
The Downing Street spokesman said that when Mrs Regan travelled with Mr Cook, it was "as the partner of the Foreign Secretary, who is estranged from his wife.
"Robin Cook has made clear that he is estranged from his wife and regards Mrs Regan as his partner. It is not unusual for the spouse or partner of a minister to go on official visits of that sort, particularly if there are cultural aspects or the host would also be accompanied."
A Foreign Office spokesman said Mrs Regan would not travel as Mr Cook's secretary but as his partner. "Her activities are synonymous with being a spouse."Her official trips would be funded from Government sources, as with other partners and spouses.Reuse content