Nick Clegg has given his strongest hint yet about the real reason Danny Alexander was chosen to succeed David Laws at the Treasury.
The deputy prime minister, who insisted yesterday the sole reason for the appointment was that his former chief of staff was "extremely gifted", told the Today programme that Mr Alexander "understands how the coalition works".
Doubts about the new chief secretary to the Treasury's lack of economic experience have clouded the 38-year-old's appointment, after Mr Laws' resignation at the weekend over an expenses scandal which also revealed a homosexual relationship.
The need to retain the balance of the coalition, by having a Lib Dem in the Treasury as well as George Osborne, meant Mr Alexander - who had originally been given the Scottish secretary job - had to be promoted to a far more prominent position.
Mr Clegg insisted that Mr Alexander was "very, very able" and would "work well" with the chancellor.
"He understands how the coalition works - to make sure that as we are entering into this very difficult period of fiscal contraction we also honour the things the coalition government has pledged to do," the Lib Dem leader said.
"That's a very difficult political balancing trick and I think he's ideally placed to do that."
Mr Clegg said Mr Laws' resignation was "personally tragic" but argued the way the government moved quickly to appoint a successor demonstrated the stability of the coalition.
"We acted very fast... government carries on and the strategy we've set out at the beginning of this government in dealing with the public finances is being worked on as hard now as it was before David Laws' departure."
"People might create a lot of synthetic anxiety around these unfortunate events, but government carries on and the strategy we've set out about dealing with the black hole in the public finances has not been interrupted in any way."