Keith Prince is a member of the London Assembly.

After a surprisingly long honeymoon, Londoners are waking up to the fact that Sadiq Khan made a vast number of misconceived or unachievable promises in order to get elected.

Last Monday our city was being crippled by a hugely disruptive Tube strike – the kind he promised would not happen on his watch.

There are numerous reasons why tube strikes should be of concern, but I want to focus on what they could mean for the prospects of rail devolution in London.

On Friday, Sadiq Khan announced that he was refusing to take up the Government’s offer to be involved in the Southeastern refranchising process. To understand why he has thrown his toys out of the pram in this way, it’s worth examining the journey that led us here.

For nearly a decade there has been cross-party support at the London Assembly for the devolution of London’s mainline rail to Transport for London.  As Mayor, Boris Johnson worked extremely hard to convince an often sceptical Department for Transport of the merits of this and in January it appeared that his hard work was bearing fruit.

The Mayor and the then Secretary of State for Transport, Patrick McLoughlin, released a joint consultation looking at how devolution could be achieved.  Unfortunately, if you were trying to design a Mayor who would do everything possible to stop devolution from happening then you could not do better than Sadiq Khan.  As a candidate and now as Mayor, his statements, actions and promises have been a masterclass in ineptitude.

If rail devolution does happen, then the Mayor, who chairs the TfL Board, becomes an incredibly important figure for the travel of millions more Londoners – and those from outside London who commute into the capital. So it is of the utmost importance that he or she proves themselves trustworthy and sensible. The Mayor is failing that test.  He has done this in five main ways.

First, he has promised the undeliverable. Last Monday’s Tube strike would be unacceptable at the best of times, but it is made worse by the fact that last February the then Labour candidate promised that should he become Mayor he would “make sure there are zero days of strikes.”  Londoners and London businesses will not appreciate this broken promise, but nor will the Department for Transport ignore it.

The second key point is Sadiq Khan’s other big broken transport promise. As Londoners returned to work in the New Year, anyone who buys a weekly, monthly or annual Travelcard or anyone who uses Pay As You Go Oyster Cards and routinely hits the daily or weekly cap will have seen their fares rise.  Once again this was in spite of the fact that last January, candidate Khan had told Londoners that if he became Mayor they wouldn’t “pay a penny more in 2020 than [they] do now.”  As well as a broken promise, the partial fares freeze that he did introduce will cost TfL £640 million over four years.  It is hard to believe that this will not put vital infrastructure at risk.

To make matters worse, Mayor Khan has continued to claim that if given control of mainline rail he would freeze rail fares.  This means that his so-called “fares freeze” has managed to be simultaneously a broken promise, a way of starving TfL of funds and a signal that there would be a real risk to entrusting control of mainline rail to TfL when Sadiq Khan chairs the TfL Board.

It gets worse. With repeated statements that he wants TfL to take over the running of Southern, Sadiq Khan has invited the suggestion that he doesn’t understand how rail devolution does or would operate.  Under the successful model for the London Overground, TfL effectively takes the place of the DfT, drawing up and tendering contracts. TfL does not run any mainline rail lines.

The fourth point is the Mayor’s repeated unwillingness to confirm that should TfL gain control of Southern Rail, the introduction of Driver Only Operation would continue.  Once again it is not hard to imagine the Department for Transport looking on in disdain as Sadiq Khan allows the suggestion to linger that he would not stand up to militant transport unions.

And that brings me to the fifth and final point: Sadiq Khan’s failure to condemn the strikes either on Southern or even on the London Underground, further underlines that he’s a liability.  Any Labour Mayor would have had to deal with the perception that they might be too close to the unions. Sadiq Khan has completely and utterly failed to do that. Thus Monday’s Industrial action saw him willing to admit that the strike is “pointless” but not to admit that it is wrong.

These failings are deeply unfortunate for London, for London businesses and for Londoners because rail devolution has the potential to radically improve mainline rail in London and the south east.

However it is hard to ignore the fact that Sadiq Khan is now the biggest obstacle to the devolution of mainline rail, not because he is a Labour Mayor but because he seems to lack any interest in persuading the Government of the merits of the case, whilst acting in such a way as to consistently undermine it.

On Wednesday, Kent County Council, which had previously backed rail devolution, withdrew their support saying, in a letter to the Mayor, that many Kent councillors “do not trust you to take control of rail services that affect our county” and that “unfortunately you gave us and people in London completely different messages about your plans.”  We’ve seen that Sadiq Khan is willing to say anything to anyone at anytime if he thinks he’ll get away with it. This time he hasn’t.

Sadiq Khan’s decision on Friday to refuse to have any involvement in putting together the Southeastern franchise is the natural endpoint of his behaviour. He’s decided that shouting at the Government and stamping his feet when he doesn’t get his way is a better bet than addressing their concerns. Sadly for Londoners, who deserve a Mayor who is willing to put their needs above his own, it is they who will lose out from Sadiq Khan’s misbegotten approach.