The BBC News director has defended the corporation's coverage of Nelson Mandela's death, after 850 viewers complained that it had devoted too much airtime to the former South African president and not enough to the storms that lashed Britain's eastern coast.

James Harding apologised to anyone who thought the corporation did not do enough about the weather on its BBC1 10pm bulletin on Thursday night but said Mandela was a man of "singular significance" and the "most significant statesman of the last 100 years".

The BBC received about 850 complaints about the extent of its Mandela coverage, including its decision on Thursday evening to interrupt a repeat of sitcom Mrs Brown's Boys on BBC1 to bring viewers news of his death.

"Firstly I'm sorry if there are people who felt we didn't inform them of what was happening in the weather," Harding told the BBC's Newswatch programme on Friday.

"The decision-making is one around the significance of Nelson Mandela. Nobody needs a lecture on his importance but we are probably talking about the most important statesman, the most significant statesman, of the last 100 years, a man who defined freedom, justice, reconciliation, forgiveness. The importance of his life and marking his death seems extremely clear to us."

BBC1's 9.30pm repeat of Mrs Brown's Boys averaged 2.8 million viewers, while the channel's 10pm bulletin – doubled in length to an hour – attracted 5.1 million. ITV's News at Ten, also extended to 60 minutes, averaged 2.8 million.

Among those viewers who complained, one said: "Major stories such as Mandela's death need to be dealt with but a balance has to be struck. His death was not unexpected, he was an elderly man who had been ill for many months."

Another said on Twitter: "BBC interrupts Mrs Brown 10 minutes before the end for a newsflash about Nelson Mandela. News at 10 could've waited!"

Harding said he "completely took" people's point about the weather but pointed out the BBC had other news services, such as local radio and online.

"But in this particular moment I thought on BBC1 we were telling people as they switched on the news as they came home that president Mandela a man of singular significance had died," he said.

"In addition to that there is a lot of news that is rolling, you are seeing president Obama come out and make comments, David Cameron make comments. The BBC and only the BBC managed to get former [South African] president FW De Klerk."

He added: "I completely take your point about the weather. What's happening in people's communities, what's happening closest to where they live matters enormously. We had been rolling weather coverage from early in the day, particularly when the storms were at the strongest."

In 1990, more than 500 Antiques Roadshow viewers complained after the BBC cut away to news of Mandela's release from prison.

Separately, Harding defended his decision to create a handful of new senior management posts in BBC News, including the newly created role of managing editor, at a time when the corporation's budget was being cut.

"In the last three or four years we have been cutting senior management within BBC News by about 30%. It is a very large news organisation and it is important it is well managed. It can't be a free-form jazz band."

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