Butler leaves after 18 months as head of the 60-strong corporate and PA arm at B-M to take up a European PA brief at the drinks giant. The move marks the latest in a string of senior jobs held since 1999, including directorships at the then Shandwick International's public affairs arm and at APCO.
He is set to join Diageo on 31 March as group external affairs director for Europe, to lead the group's regulatory and PA strategy across the EU.
The group said this week he would be playing 'a key role in addressing issues such as self-regulation of advertising and marketing and EU excise duty'.
Butler will report into Diageo group external affairs director Mark Leverton.
B-M said it will not be replacing Butler, instead handling his responsibilities to remaining client managing partners Gavin Grant and Kate Triggs, who will head the PA and corporate teams respectively.
B-M UK chief executive Allan Biggar said: 'We are just being prudent in the current climate. We don't want to have lost a senior team player, but if we can manage it internally, that's prudent at the moment.'