You have 2 more free articles remaining

That it has survived almost two millennia buried and then excavated is almost as remarkable as its construction. Small wonder then that when it was bought for £520,000 by the British Rail Pension Fund at Sotheby's in 1979 as the star of the collection formed by Mr and Mrs Andrew Constable Maxwell, it set an auction record price for a piece of glass that stood for over nearly 20 years. Indeed that record was only broken when the cup next came up for sale, as part of the pension fund's ancient glass collection at Sotheby's in 1997, when it raised £2.1m. On that occasion it was secured by a telephone buyer who proved to be the chief talking point of the auction not just because they purchased the cage cup but because they hoovered up no fewer than 11 of the 33 lots, providing around 90 per cent of the £3.6m total.

Looking at their 11-lot tally, the buyer's taste appeared to be for well-shaped pieces with relatively little restoration, and in their determination to secure them they beat off considerable opposition and paid prices that were far in excess of the estimates.

There was much speculation at the time about who this big spender might be. Since then we have become more used to this type of wholesale domination of an auction, most often as a sign that the world's big collector, Sheik Saud of Qatar, is in action.

Whoever the mystery buyer was, seven years on, the 11 lots they purchased are to come up for sale again, this time at Bonhams Bond Street in a special single-owner 24-lot evening auction on July 14. The other 13 lots are a mix of Pre-Columbian, Egyptian and other antiquities, another piece of ancient glass and a 19th century Turkish jewelled zarf or cup holder.

With the exception of the latter, which was acquired in 1980, all the pieces seem to have been purchased in London or New York auctions in something of a spending spree between 1997 and 1998 (the non British Rail ancient glass entry, a Roman cameo glass skyphos, was purchased the day after the pension fund sale at Christie's in London for £450,000).

Interestingly, it seems the vendor is not necessarily expecting the prices at Bonhams to equal the substantial sums that they gave to acquire them in the late 1990s. Many of the estimates reflect the levels at which they were then guided, not the substantial sums they paid. Accordingly, the Constable Maxwell cage cup, as it is still known, is guided at £1.5m-2m; the 4th/5th century AD Anglo-Saxon glass bucket, which cost £185,000 in 1997, carries an estimate of £70,000-90,000, while the cameo glass skyphos from Christie's is estimated at £100,000-150,000.