Here's an update direct from the on-site contract manager:
Several leaks have been discovered in the low pressure gas mains around the Foxley Hill Rd / Godstone Rd junction and some gas has been detected in ducts belonging to BT, Virgin & UKPN. The leaks have been fixed but it's taking time for the concrete to cure and to ventilate the ducts. This work should finish by Friday, but SGN suspect that there are also leaks in the plastic medium pressure pipeline running along Godstone Rd which was installed only 20 years ago. If their fears are confirmed then it could be another two weeks till 23/9 before this is also fixed.
SGN is as keen as anyone else to get this fixed ASAP because they're incurring fees of £3000/day from TFL, but they can't work any faster.
Obviously the huge traffic jams are extremely regrettable and causing massively increased pollution, but it just can't be helped. I have the phone number of the engineer in charge, and he's promised to update me if there is any change in the situation.
Cllr Simon Brew