Prince Jefri Bolkiah of Brunei bought Asprey, the Queen's jewellers, and the imperial state crown of King George I, dated 1715, the coronation crown of King George IV, 1821, and the coronation crown of Queen Adelaide, 1831, last month.
The crowns, and the Bible on which George III swore his coronation oath, were thought to be the subjects of a bidding war between American dealers.
The prince announced that he was presenting the treasures, worth an estimated pounds 1.7m, to the nation after a campaign against their possible sale to foreign dealers.
A spokeswoman for the prince said: "Prince Jefri has reluctantly decided to make his decision public since in recent days Asprey has received a number of serious offers for the crowns from private individuals."
The prince, who paid pounds 243m for Asprey, is expected to win the support of art historians who have criticised the Government for not doing more to keep the crowns in Britain.
Last July, the Heritage minister, Lord Inglewood, deferred a decision on granting export licences for the artefacts until January. The Sultan of Brunei's family are known to be strong Anglophiles and have at least five large homes in London. The present Sultan's father also built a museum in honour of Winston Churchill in Brunei's capital Bandar Seri Begawan.
The country's links with Britain go back to 1847 when the Sultan signed an agreement to suppress piracy and 41 years later Brunei became a protectorate. The links between the two countries were cemented in 1962 when there was an uprising following the persistent postponement of a democratic assembly. Gurkhas were called upon to suppress the uprising and they have stayed ever since, although the country has been independent since 1983.
The family now spends lavishly on their loyal subjects who receive free education, free health care, almost free housing and no taxes. The Sultan is reputed to be worth at least pounds 30bn, generated from the country's oil and gas fields.
Prince Jefri's extravagance is legendary. When he stays at his brother's London hotel - the Park Lane Hilton where suites cost about pounds 1,000 a night - he books three floors. He is also reportedly negotiating to buy MI5's former central London headquarters. The price is believed to be pounds 50m.Reuse content