Londoners were hit with fresh Tube misery this morning as a series of rush-hour problems hit the transport network.
Signalling failures saw a part suspension on the Jubliee line, while Metropolitan line trains were held up at Baker Street and Finchley Road.
Another signalling problem, at Caledonian Road, led to delays on the Piccadilly line, and a faulty train at Piccadilly Circus added to the Monday morning chaos, causing severe delays on the Bakerloo line
It was the latest in a string of morning disruptions on the London Underground which will be launching all-night services in September.
Mick Cash, general secretary of the RMT transport union, said: "The engineering and fleet issues that have arisen yet again on this Monday morning are a massive reminder of just how challenging the environment is for the teams of staff out there day and night keeping London moving.
"Those challenges will be ratcheted up by the plans for night running, plans that the politicians say they now want to extend across the system and on to London Overground."
Nick Brown, London Underground's chief operating officer said: "I apologise to customers for the disruption they've suffered this morning on some Tube lines due to problems including signal failures and faulty trains.
"Our engineers are working as quickly as possible to restore services on the affected lines. We will be refunding customers who were affected by the disrupted services this morning."
