I was told to expect a statement from Thames Water about the situation at Wembley Triangle yesterday but none was forthcoming by midday today so I tweeted them at midday. The incident began on Thursday. LINK
Their answer is above.
UPDATE - Neil Levy of Thames Water has sent the following message:
We managed to work all night yesterday to repair the sewer and we have demobilised from the site now.
We found that the sewer was severely blocked with rubble, bricks and fat, which we believe may have caused a break in the pipe.
We have restored the sewer service and there has been no further flooding or pollution impact to the environment.
We apologise for any inconvenience this has caused but traffic should be back to normal by the end of today.