On the UN Climate Summit, Desmond Tutu has said that we all have a "duty to persuade our leaders to lead us in a new direction"
The Archbishop emeritus of Cape Town and a Nobel peace laureate was writing in the Observer.
David Cameron, anti-apartheid leader Desmond Tutu and Prince Harry have a led a memorial service for former South African president Nelson Mandela.
Harry, who was representing the Queen, was joined by senior politicians including the Prime Minister and Labour leader Ed Miliband at a Westminster Abbey service celebrating the life of Mandela, who died on December 5 aged 95-years-old.
Nearly 2,000 people attended the service which featured South African singing and drumming and an address to the congregation by the country's deputy president Kgalema Motlanthe.
The Most Rev Tutu, the former Archbishop of Cape Town, also made a speech and thanked the "splendid" and "amazing" anti-apartheid campaigners for their efforts in changing the "moral climate" over apartheid.
He said: "What would have happened had Mandela died in prison as was the intention and hope of the upholders of apartheid. I suppose most would have regarded him as no better than a terrorist - after all, persons in high positions in Britain and the US did dismiss him as such."
Archbishop Desmond Tutu is giving a blessing to bring the memorial service to a close.
He begins: "I stand here as an old man and I want to remind you that we got to this point because we were disciplined. So I am not going to give you a blessing until all of you stand."
"I want to hear a pin drop," he exhorts, before looking all around him to check that everyone is standing.
"You must show the world that we are disciplined," he says.
Twitter has reportedly apologised after suspending official the account of the Desmond and Leah Tutu Legacy Foundation during a 'spam clear-up.'
The account was only started overnight and within hours had been suspended.
The Foundation has said that Twitter had apologised for the mistake and the account is now working again:
Archbishop Desmond Tutu, 81, has been admitted to a hospital in South Africa for treatment and tests related to an ongoing infection.
"Archbishop Emeritus Desmond Tutu has checked into a Cape Town hospital for the treatment of a persistent infection and to undergo tests to discover the underlying cause.
"He was in good spirits and full of praise for the care he receives from an exceptional team of doctors. The non-surgical treatment is expected to take five days," his foundation said in a statement.
Archbishop Desmond Tutu has been awarded a £1.1 million prize for "affirming life's spiritual dimension".
The 81-year-old landed the 2013 Templeton Prize for his lifelong work in advancing spiritual principles such as love and forgiveness which have helped to liberate people around the world, organisers said.
The former Anglican archbishop of Cape Town said: "When you are in a crowd and you stand out from the crowd it's usually because you are being carried on the shoulders of others.
"I want to acknowledge all the wonderful people who accepted me as their leader at home and so to accept this prize in a representative capacity."
The Templeton Prize has been the world's largest annual monetary award given to an individual for the past 40 years.
One of the biggest campaigns in a decade to end world hunger is being launched today, by a hundred charities across the UK.
Talking about the IF campaign to ITV Daybreak, Brendan Cox explained how previous campaigns have made amazing progress, but the one area that does need work is hunger.
He said the world's food supply needs to be redistributed and the G8 could be the moment the UK 'turns the tide' on this.
A campaign to end world hunger and poverty is being backed by charities and celebrities across the UK.
The 'Enough Food For Everyone If' appeal is the biggest attempt in almost a decade to try and end world hunger.
Celebrities such as pop band One Direction, Actor Orlando Bloom and Newsreader Natasha Kaplinsky have appeared in an advert about the campaign.
Multi charity coalition IF claims that tackling the 'corporation tax gap' by multinational companies could help developing countries to raise enough revenue every day to save the lives of 230 children under five.