The Jewel Tower, built in 1365, is one of only three buildings of the medieval Palace of Westminster which have remained more or less intact. The other two are Westminster Hall and Inigo Jones' Banqueting House. Its full glory has only recently been revealed because from the 17th century until the 1960s the Jewel Tower - located at the back of Westminster Abbey opposite the House of Lords - had buildings around it on three sides blocking the view to the general public. There were fears in the 19th century that it was only a matter of time before it was demolished.

As Augustus J Hare (1834-1903) observed: "It will scarcely be credited by those who visit it that the destruction of this interesting building is occasionally in contemplation and that the present century for the sake of making a regular street will perhaps bear the stigma of having destroyed one of the most precious buildings in Westminster which if the houses around it were cleared away and it were preserved as a museum of Westminster antiquities would be the greatest possible addition to the group of historic buildings to which it belongs."

Survive it did. First, under Edward 111 (1312-1377), as a repository for the royal jewels and later as storage for official documents. When document storage was moved to the newly built Victoria Tower in 1869 the Jewel Tower became the place where official weights, measures and volumes for the whole of the British Empire were tested - including the volume of a pint of beer. This lasted until the arrival of the motor car and the construction of Lambeth Bridge when the resultant vibrations proved too much for such a delicate operation.

The lawn in front of today's Tower is roughly where the King's garden was in the private section of the Palace. Not that Edward was there very often. He had other homes to go to at Windsor, Eltham and Sheen. Only the Norman kings stayed regularly at Westminster so they could make a quick getaway down the Thames if the going got rough.

If you enter the ground floor room to pay your admission fee today and have a cup of coffee in the café, it would be easy to miss the beautifully constructed vaulted ceiling which wouldn't look out of place in a cathedral. The first floor has a stone vaulted ceiling installed in the 1750s as a fire precaution while the second floor looks much as it did in medieval times with a 14th century door and a wooden ceiling installed in 1949. The rectangular framed windows in the turret on the north (Abbey) side were almost certainly designed by Nicholas Hawksmoor as they are similar to other work he has done. He was Clerk of Works at Westminster where he designed the western entrance to the Abbey and lived in nearby Millbank.

Looking at the Tower from the road you can see the remains of a moat once used as a fishpond - beside which the drain from the Abbey ran to the river. The remains of the old fortification wall can also be seen protruding from the Tower.

Little known fact: The space to the left of the Jewel Tower, between the Tower and the old Abbey wall, was where prime ministers used to park their cars.