Downton Abbey's controversial rape storyline will not be formally investigated by Ofcom, the regulator has announced.

The episode which saw Joanne Froggatt's character Anna Bates attacked in the kitchens by a visiting valet, played by Nigel Harman, drew 244 complaints to Ofcom, and a further 200 to ITV.

But Ofcom has said it has decided not to pursue the complaints "after careful assessment... because they did not raise issues warranting investigation," the BBC reported.

Downton Abbey is broadcast at 9pm, after the watershed, but is generally accepted as light Sunday night entertainment.

A warning alerting viewers to the upsetting scenes was broadcast before the episode, which was seen by an audience of almost 12 million.

An Ofcom spokesperson said the warning had been taken into account, as well as the fact the show aired after the watershed.

The fact that the attack itself took place off-screen also played a part in the regulator's decision.

Writer Julian Fellowes and the stars of the show have said they felt proud to be tackling the subject.

Although Joanne confessed: "We all expected there to be a certain controversy when we tackled that subject matter, but I didn't expect it to be quite as controversial as it has been."