Three royal crown frames not seen by the public this century will go on display in the Martin Tower - the 1715 George I crown, the Coronation Crown of King George IV (1821) and the Coronation Crown of Queen Adelaide (1831).
Alongside the George IV crown will be a pounds 2.5m pile of 12,314 diamonds, lent by De Beers to represent the number of diamonds originally set in the frame. Before De Beers and its predecessors started mining diamonds in South Africa in the 1800s, the gems were so costly that monarchs generally hired a set for their coronation. George IV faced a hire charge of pounds 65,000.
The "Crowns and Diamonds" permanent exhibition which opens to the public on Thursday is something of a homecoming. For 200 years the Martin Tower was known was the "Jewel Tower" because from 1669 the regalia were displayed in its lower chamber.
In 1671, the Tower was the scene of the only successful attempt to steal the Crown Jewels. Colonel Blood and his accomplices overwhelmed Keeper Talbot Edwards and seized the State Crown, Orb and Sceptre. They were caught attempting a getaway, but after a brief spell in the Tower, Blood was pardoned by Charles II.
The Imperial State Crown of George IV was wrenched out of shape when a "deranged woman" tried to snatch it through a grille. It is the oldest surviving English state crown.
The three frames - discarded by the monarchy more than 100 years ago - were given back to the Queen's collection this year by Prince Jefri Bolkiah of Brunei who acquired them when he bought Asprey, the Bond Street jewellers.