Boris Johnson has blamed today's tube strike on union leaders trying to "flex their muscles" following the death of Bob Crow.
This may well be true. Transport for London's plans to close ticket offices are likely to go ahead, no matter what RMT chiefs may tell their members.
However, union bosses are not the only people guilty of making big promises they can't deliver on.
Take these rather whopping pledges made by Boris over the past six years.
"I will stop the planned ticket office closures" - Boris Johnson's manifesto 2008
Boris Johnson ran for mayor on a promise to oppose all London underground ticket office closures.
This was a cast iron pledge which he even signed 'Nick Clegg tuition fee style' in front of the cameras.
He would later repeat this pledge, telling the London Assembly: "The first and most important point to make is that no ticket offices will be closed, alright? They're not going to be closed"
Pushed on the point he went on to say that: "The answer to the number of ticket office closures is: nil."
It would later turn out that the answer to the number of ticket office closures was "all of them".
"Every station that has a ticket office will continue to have one." - Boris Johnson, 2010
When it became clear that he did have plans to close some ticket offices, he quietly ditched this promise in favour of a new pledge that all stations that had at least one ticket office would retain one.
"This mayor takes his promises to Londoners extremely seriously. Every station that has a ticket office will continue to have one," his spokesperson told me at the time.
This continued to be his policy right up to and throughout the last mayoral election.
It was only after he was elected, that he abandoned this pledge along with similar pledges not to close police or fire stations. It is these broken pledges above all else which have caused the series of strikes we've seen in London over the past few years.
"I will seek to negotiate, in good faith, no strike deals with the Tube unions to end the disruption caused by unnecessary strikes" - Boris Johnson transport manifesto 2008.
Boris's most outlandish promise of all was his 2008 pledge to forge a "no-strike deal" with the tube unions.
In one election leaflet he promised to "deal once and for all with endless Tube strikes" by negotiating a "no strike deal with the unions".
This promise was also included in his manifesto.
Six years on and he has still made absolutely no progress on this promise. Indeed Johnson has not even sat down with union bosses once in order to try to negotiate such a deal.
Once it became clear that his no-strike deal was a non-starter, Johnson instead turned his attention to banning tube strikes instead.
For several years Johnson called on the coalition government to introduce new "minimum turnout" laws, forbidding any strike action where fewer than 50% of members turned out to vote.
This idea was immediately mocked by the unions who pointed out that Johnson had been elected twice on turnouts far below 50%.
However, Johnson persisted with the idea and confidently predicted that he would secure agreement from the government.
In his 2012 manifesto he insisted that "this election will give me a fresh mandate to secure legislation from No. 10 to introduce the minimum turnout rule."
However, despite the occasional warm words from anonymous "government sources" over the years, there are currently no plans to introduce a minimum turnout rule during this parliament.
Even Johnson has acknowledged this, telling the London Assembly last year that: "We had high hopes that the coalition would take this up but it has not been possible to persuade the government to go even for the moderate proposal of a 50% turnout threshold.
"We’ve made this case repeatedly to government at all levels. Occasionally we have heard some favourable mutterings from the oracle, but nothing has ever really been produced."
So there you have it. The occasional favourable muttering from government, the occasional flexing of muscles from City Hall, but after almost six years in office, the tube unions are still regularly on strike and Johnson's plans to deal with them "once and for all" have come to precisely nothing.