According to BBC News:
He told BBC Look East he made his decision to stand after "an awful lot" of soul-searching in a period of "complete exhaustion" after the election.
But he concluded he should do it, he said, as "obviously the party suffered devastating results last Thursday. It's critically important that we reconnect and... have an effective advocate for what modern liberalism is all about."
He added: "As health minister I put body and soul into it and I would do the same for this job."The first online evidence of his campaign is the Twitter account Lamb for Leader, which has retweeted an impressive number of endorsements this evening.