Reports indicate that the Conservative London Assembly members have walked out of the debate about Blackfriars Bridge safety, rendering the meeting inquorate, thus ensuring the debate did not happen.
The walkout is apparently a tactic they've used before, on ticket office staffing. Somewhat ironic, considering they don't like Tube workers walking out of their jobs.
Presumably the Tories have gambled that taking their ball home is less politically damaging than losing the match (which they were going to do), the consequence being that Boris would've had to go against the Assembly's recommendation. It's now up to people who want Blackfriars Bridge to stay 20MPH to ensure that the issue is brought back into play as soon as possible.