London Underground delays to be examined
A "thorough investigation" into why weekend engineering works on the Tube over-ran causing thousands of people to be delayed is set to be carried out.
On Monday morning, passengers were delayed as work to replace track in the Neasden area was still taking place.
The Metropolitan line was suspended between Harrow-on-the-Hill and Aldgate, while the Jubilee line was down between Stanmore and Willesden Green.
London Underground said engineers were working flat out to restore services.
Chief operating officer Howard Collins said rail replacement buses were running.
Passengers trying to get round the problems by switching to the Piccadilly line then ran into more problems, when a faulty train at Rayners Lane led to severe delays between South Harrow and Uxbridge.
Those trying to avoid the problems were also hampered as the Overground and Bakerloo services in the Queen's Park area also faced delays.
Transport for London said it would be thoroughly investigating why weekend work was delayed.
Howard Collins, chief operating officer of London Underground, said: "Engineering works to replace more than half a kilometre of track this weekend over-ran which mean the Jubilee and the Metropolitan lines were part suspended this morning.
"I would like to apologise to passengers who were affected by the delay in services."
To add to a morning of upheaval on the Tube, the last part of the rush-hour was affected by a signal failure at Brixton in south London which led to delays on the Victoria line.