Prince William is set to inherit an estimated £10million from this mother's estate today as he celebrates his 30th birthday.

The milestone means he now has the option of taking control of half of a trust fund believed to be worth more than £20million.

Princess Diana bequeathed the trust to the Duke of Cambridge and his brother, Prince Harry, who were 15 and 12 at the time of her death in 1997.

Harry will inherit his share on his 30th birthday on September 15, 2014. Diana left a net estate of £12,966,022 after inheritance tax of £8,502,330 was deducted.

It is widely believed that with shrewd investment the fund has grown to around £20m.

Her estate comprised stocks and shares, jewellery, cash from her £17million divorce settlement, dresses and other personal belongings at her Kensington Palace apartment.

Diana stipulated that it would be held in trust to be shared equally between her two sons, even though William will inherit income from the Duchy of Cornwall estate when he becomes Prince of Wales.

In her original will, drawn up in 1993, the princess had stipulated that both princes would be entitled to their entire share of the capital on reaching 25.

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