Seven people were killed and 21 others badly hurt in the November 2016 crash.

Tram Operations Limited (TOL) has also been fined £4m.

TfL and TOL both accepted failings in their health and safety duties.

The tram, carrying 69 people, was travelling at three times the speed limit and topped over a sharp bend when it derailed.

In June, the tram's driver Alfred Dorris was cleared of failing to take reasonable care at work.

The 49-year-old had blamed the crash on external factors including poor lighting and signage.

The people who died were Dane Chinnery, 19, Philip Seary, 57, Dorota Rynkiewicz, 35, Robert Huxley, 63, and Philip Logan, 52, all from New Addington, and Donald Collett, 62, and Mark Smith, 35, both from Croydon.

In a filmed sentencing at the Old Bailey on Thursday, Mr Justice Fraser also ordered TfL and TOL each pay £234,404 in costs to the prosecuting authority, the Office of Rail and Road, and a victim surcharge of £170.

He told the court: "This was undoubtedly an accident waiting to happen, quite literally."

There was a failure to heed warnings about the risk of drivers becoming disorientated in the Sandilands tunnel network on the approach to the curve, and a report of a "near miss" just days before the crash was "ignored", he said.

The "complacency" around the inadequate lighting and lack of visual cues in the tunnel was "disturbing", the judge said.

Prosecutor Jonathan Ashley-Norman told the court the main failing of the operators was to make a suitable risk assessment of such a high-speed derailment happening.

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He said there were "missed opportunities" over the years to take a closer look at the Sandilands curve but action was not taken.

There was "over-reliance on fallible humans" and tram drivers were "let down" by their employer TOL, and by TfL, the court was told.

London's Transport Commissioner, Andy Lord, said: : "I apologise on behalf of everyone at Transport for London, both past and present, for this tragedy and for the pain, distress and suffering that all those affected have endured and continue to endure.

"Every passenger on the tram that morning entrusted their safety to us but we failed them and for that I am truly sorry. We remain committed to providing support to anyone who needs it."