The films form part of the public exhibition of the Princess' life when the Earl opens the Althorp estate to the public in July.

It also features in a BBC documentary, Diana: My Sister, the Princess, to be broadcast before the estate is opened.

Earl Spencer: "Smallest things leads to tears"

Speaking to the BBC's Radio Times, Earl Spencer said: "It was really sad, really sad, to see this little girl running around and to know what happened to her when she became older.

"I find it very difficult to talk about Diana. I find that the smallest thing will set me off crying."

The Earl singled out one film showing the late princess laughing in a boat.

"Although it was silent, I could really hear the laugh," he said.

"It was such a joyous laugh and I will never hear that again."

The exhibition of Diana's life will be open to the public from July 1, what would have been her 37th birthday, until the eve of the anniversary of her death, August 30.

Diana: Fears of Althorp shrine

Around 150,000 people have paid £9.50 each to see the museum but they will not be allowed onto the island where the princess is buried.

Nearby villagers have criticised the Earl's plans, saying they fear a deluge of tourists.

There have also been fears that Althorp will become an English 'Graceland', a shrine to Princess Diana similar to the former Memphis home of Elvis Presley.

But the Earl said he hoped the exhibition would not be a morbid experience.

"In the last film and the last room that people go into she is presented as really happy," he said.

"We don't want people to come here and just be miserable."

MP opposes memorial garden

Meanwhile, Kensington's MP Alan Clark has said he is "completely opposed" to government-led proposals for a multi-million pound memorial garden to Princess Diana in the royal borough.

Clark: Pledged to campaign for residents

Around 1,000 people at a public meeting heard the controversial MP say he would support attempts to stop the creation of the gardens in the grounds of the princess' former home, Kensington Palace.

Residents of the exclusive London borough fear up to five million tourists will flood Kensington, leading to more traffic, environmental damage, souvenir traders and fast food stands.

Mr Clark, who had previously urged a more neutral line over the gardens, said: "I am complete in my mind about what my constituents want."