EXCITEMENT surrounded the smuggling of a £4 million casket rumoured to have once contained relics of St Thomas Becket into Canterbury Cathedral.

The exquisite 12th century casket was transported from its home at London's Victoria and Albert Museum and sneaked into the Cathedral in amid maximum security.

Only invited members of the Press were aware of the low key arrival of the precious antique, which went on public display on Saturday with other items related to St Thomas including a tiny fragment of his bone.

After being painstakingly unwrapped and displayed for photographers, the casket was put on display behind a secure glass cabinet where it will be the subject of massive security throughout the two-week display.

The casket, now empty, was bought by the Victoria and Albert Museum in 1996 for £4,286,038 after a vigorous campaign by the National Art Collections Fund.

It is on loan to the cathedral for display in the Treasury until June 27 as part of nationwide year-long celebrations of the Art Fund's centenary.

The elaborate blue and gold enamel casket dating back to 1180-90 is a magnificent example of late Romaneque art.

It is said to have contained a relic of St Thomas Becket, murdered in the Cathedral in 1170 by four knights who believed they would please Henry II by doing so.

In fact it is doubtful whether this particular casket, which was originally at Croyland Abbey near Peterborough until the Reformation, or similar ones at churches throughout the country did contain the authentic relics of the saint.

Experts say so many churches claimed to have relics that there could not have been enough of him to go round.

In fact curator of the Treasury at Canterbury Cathedral Susan Hare believes the real St Thomas could still be buried and the bones Henry VIII later ordered to be burned were those of an anonymous replacement monk.

"Henry VIII insisted the bones were burnt and thrown to the winds, so determined was he that the veneration of St Thomas Becket would be gone forever.

"But did the monks bury him somewhere else? I think they realised what would happen and substituted his body for a nameless monk.

"It became a point of veneration for churches to have a casket which they could say had bits of his relics in.

"Limoges specialised in making these caskets. Nobody knows if the casket really had his relics in - again, it depends if any of the relics were actually those of St Thomas in the first place.

"The real value of it lies in the beautiful scenes of his death and the workmanship that has gone into it."

Other items on display include the Hubert Walter Chalice and Paten which were in use at Canterbury Cathedral at the time of St Thomas and which he may well have used, a tiny two millimetre fragment of bone said to be his, and a buckle from St Thomas's shoe.