London had trumped competition from Manchester and cities in Germany to win the right to host the cycling race's Grand Depart in 2017 - but Transport for London announced last night it had pulled out after weighing up the costs involved.
Johnson explained that the £35m it would cost to host the event could be better spent elsewhere - including safer cycling lanes - and said the final decision to decline the race rested with him.
I had to take a very tough decision, obviously painful. In an ideal world, you know me, my policy is to have your cake and eat it.
The difficulty was we had to make a choice - £35m is an awful lot to spend on a one off event when you could put that money in to long term projects. What people really want is safer cycling lanes.
Race organisers Amaury Sport Organisation (ASO) have now awarded the event to Germany.
The £35m fee would cover a direct payment to ASO and the costs of managing extensive transport disruption to the city.