Image copyright PA Image caption It is nearly 20 years since William and Harry lost their mother, Diana.

Prince William and Prince Harry have attended a private service to rededicate the grave of their mother, Princess of Wales, almost 20 years after her death.

The service was held at Diana's family home in Northamptonshire on what would have been her 56th birthday.

The ceremony was also attended by the Duchess of Cambridge, Prince George and Princess Charlotte.

Prince Charles and the Duchess of Cornwall are in Canada.

The service, at Althorp House, was conducted by the Archbishop of Canterbury, Justin Welby.

The Princess of Wales died on 31 August 1997 in a car crash in Paris, when the Duke of Cambridge was 15 and his brother was 12.

Analysis

Image copyright Reuters

By Peter Hunt, royal correspondent, BBC News

This is the start of a difficult few months for Prince William and Prince Harry as they remember their mother who, they say, smothered them in love.

They were traumatised children when she died.

Harry has spoken of how he shouldn't have been made to walk behind Diana's coffin.

William has expressed his considerable regret that they weren't old enough to do more to protect her.

Twenty years on, together, they're taking control of how she will be remembered.

They've commissioned a statue. Its unveiling, in the future, will be public.

Today's service was to be very private, with no media present.

The princes, like their mother, have a complex relationship with the press.

They will never forgive the paparazzi who pursued their mother's car in Paris.

Also absent from the graveside was Prince Charles.

It's fortuitous he's in Canada and it's probably a relief for all concerned.

Read more from Peter Hunt

The princes have commissioned a statue of Princess Diana to mark the 20th anniversary of her death.

The sculpture will be placed in the public grounds of her former residence, Kensington Palace.

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