Prince Harry has spoken for the first time of his determination to keep alive the memory of his mother Diana, Princess of Wales.

The prince, who celebrates his 18th birthday on Sunday, has vowed to "finish" his mother's charity work saying she had "more guts than anybody else".

Princess Diana campaigned against landmines

In an interview to mark his coming of age, he said he wanted to follow in her footsteps and admired the way she reached out to the vulnerable.

"The way she got close to people and went for the sort of charities and organisations that everybody else was scared to go near, such as landmines in the Third World.

"She got involved in things that nobody had done before; Aids for example," he said.

I want to carry on the things that she didn't quite finish

Prince Harry

Prince Harry, whose mother was killed in a Paris car crash just three weeks before his 13th birthday, hit the headlines earlier this year when it was revealed he had been drinking under-age and experimenting with cannabis.

He says that sort of behaviour is now behind him.

"That was a mistake and I learned my lesson. It was never my intention to be that way."

Honouring her memory

The young prince, who is third in line to the throne, carried out his first solo engagements last Thursday in London - meeting drug addicts, homeless children, and those who suffered abuse.

He also paid a special visit to meet children suffering from leukaemia at Great Ormond Street hospital in London.

Harry received a birthday gift at hospital

Prince Harry said he was 15 or 16 when he first considered following in his mother's footsteps.

"I always wanted to do it, but especially after my mother died.

"The fifth anniversary of her death was important because she wasn't remembered in a way I would have liked."

The prince is believed to have been upset by a book written by former royal bodyguard Ken Wharfe about Diana's private life and romantic affairs.

He said he would have liked to emphasise more positive aspects of his mother's life.

"I want to carry on the things that she didn't quite finish. I have always wanted to, but was too young."

His first duties included a trip to West Ham

But he admitted that his first solo public engagements had been quite daunting without the support of his father and brother.

"It was quite difficult at first, being younger and not as experienced as some of the people I was meeting," he said.

"I have seen my mother doing it so many times and she was so good at it."

Prince Harry has also posed for seven portraits to commemorate his 18th birthday, with Diana's favourite photographer, Mario Testino.

Proceeds from their sale will go to Merlin, a small charity that funds health care in developing countries.

'Quiet birthday'

Although Prince Harry is beginning to raise his public profile, he turned down his father's offer of a big birthday bash, preferring instead to celebrate at home in Highgrove, Gloucestershire.

He said: "I don't actually like being the centre of attention.

"Plus, there's all the organisation I would have to do, and I've got school the next day. So it will be a quiet day at home with my father and my brother - my family."

Academic work means the prince, who started his final year at Eton last week, will take on charity work gradually.

He may possibly take a gap year to travel after his A-levels, before university or the armed forces.