Further to my post this morning, my office has been in touch with Severn Trent who have confirmed that this morning’s traffic was not related to their roadworks, with their infrastructure having been cleared away by Monday morning.
Highways England, at my request, have investigated the traffic light sequencing and have ruled that out as a cause.
It turns out that a litter picking operation by a neighbouring local authority seems to have had a serious knock-on effect on the traffic.
The works have now been removed and the problem should not recur.
Please let me know if any further issues arise.