What a nightmare!" There had been delays involving Clapham Junction earlier in the rush hour due to a lineside fire which caused hold-ups to services on London Overground.
Polymetal - lifted in recent days by talk of a possible merger with Polyus Gold - lost 22p to £10.88 as it warned there was a chance it could miss its production target of 1.2m troy ounces of gold in 2013 due to delays at a Russian plant.
Passengers affected by rail delays are now able to receive cash compensation instead of vouchers, in a major change to policy by operators.
National Grid announced it was close to signing up three power stations to help fill the gap left by closures, breakdowns and delays, and said the cost to consumers of paying for extra capacity and for companies to adjust their consumption if necessary will be about £1 per household.
East Coast had a reduced service from Edinburgh to Newcastle, with possible delays.
The number of instances of "bed-blocking" was the same as the last week, with 4,000 hospital beds unavailable for incoming patients because of delays in transfers of occupants to care elsewhere.
Rush-hour passengers on a trouble-hit commuter route in the south of England have faced more disruption, with delays and cancellations because of a broken rail.
As season ticket-holders came to terms with increases of up to 2.5%, passengers on a main London to Scotland route endured delays throughout the rush hour.
Cameron has been facing questions about delays and redactions to the Chilcot report as US and UK intelligence agencies come under increasing scrutiny over the methods they use to prevent terrorism.
"We have let a lot of people down," he said and blamed the delays to the engineering works at King's Cross on equipment breakdown.
He added: "I'm deeply sorry for the delays, upset and upheaval caused today to passengers impacted by our overrunning improvement work outside King's Cross.
