Actually that is not quite true, mike.
By far and away the biggest beneficiary of the second choice votes was Brian Paddick (LibDem) who received 37.66% of those second choices. However, the London Mayoral election is different to the AV system proposed for Parliamentary elections. In the London vote if no candidate receives 50% of the first choice votes all the candidates from third place down are immediately eliminated. The second choice votes of people who voted for those candidates are scrutinised and if they are for either of the two top placed candidates then those votes are added to their first choice votes. Boris received just 124,977 second preference votes (7.34%) and Ken 135,089 (7.93%) and the 10,000 or so difference scarcely affected the result. It matters not because under this system he was eliminated after round one, but Paddick finished only 2% behind Livingstone and 7% behind Johnson when his second choice votes were added.
If the London election had been held under the AV system proposed for Parliament the outcome may have been very different indeed. The candidates finishing in third and fourth places (Paddick and Sian Berry, Green) polled almost 60% of the second choice votes between them. Assuming that people voting for the lower placed candidates as their first choice may have been unlikely to vote for either of the two main contenders there is a strong likelihood that the second choice votes (which attract equal weight to first choice votes) may well have enabled one of those two to win the election And they were the first choice of just 9.8% and 3.2% of the electorate respectively.
Would that have been fair? I think possibly not. But such are the vagaries of what I consider to be the gross unfairness of the proposed AV system where some people get two or more votes, but those choosing the first round winners are denied such a privilege.