Former South African president Nelson Mandela gave BBC One's Ground Force team their greatest challenge yet - when they gave his garden a makeover.

The show's three presenters - Alan Titchmarsh, Tommy Walsh and Charlie Dimmock - travelled to Mr Mandela's home in Qunu, in the country's Eastern Cape province for the show's millennium special, to be broadcast next month.

Help for the tricky task came from Mr Mandela's wife, Graca Machel, and one of his closest friends, former political prisoner Ahmed Kathrada.

Alan Titchmarsh said it was an ambition come true for the Ground Force team.

"This is one garden I would never have dreamt I'd find myself making," he said.

"Nelson Mandela is one of the world's most inspirational figures. His struggle has been a lesson to us all and I was particularly struck reading in his memoirs how important gardening became to him during his imprisonment.

"We were all incredibly excited and a bit nervous about this transformation. Pulling it off is a real once in a lifetime moment for everyone."

The trio managed to gain access to Mr Mandela's home for three days when the former leader, who left office in June, went on a short trip to the US.

When he returned, he was led back into his home by his wife, who had kept the exercise secret from her husband.

He was thrilled - and surprised she had kept it from him. "We're not supposed to have any secrets," he told the team.

The special will be shown on BBC One at 2015 GMT on 2 January.