Michael Parkington was charming, witty, cunning and egotistical - according to both friends and rivals. He was also one of the world's foremost glass collectors. As the fruit of his mania goes under the hammer next week.

Even if you cannot attend the sale, be sure to buy a catalogue for South Ken's auction of the biggest-ever private collection of British art glass, a comprehensive 525 lots spanning three centuries. Complete with post- sale price sheet it will be an invaluable market guide, especially to the largely uncharted later Victorian engraved glass.

Hide it in your pocket when trying to decide whether those perplexing, multi-coloured vases and glasses in boot sales and markets are junk or worth hundreds. In fact, South Ken is considering re-issuing the catalogue with prices replacing estimates.

The glass collector Michael Parkington, who died in 1994 aged 71, was a solicitor who developed a passion for British glass while in South Africa defending Nelson Mandela on treason charges in the early Sixties. He was a towering figure, charming, witty and cunning and was an insatiable buyer who paid dealers top prices and intimidated glass enthusiasts in the saleroom.

The antique dealer Richard Dennis, Parkington's London buying agent, says: "The sale catalogue will be a marker: traders will say: 'Look, it's pounds 600 in Parkington - I'll let you have it for pounds 500.'"

It is Parkington's taste for 19th century names such as Varnish and Apsley Pellat and 20th century names such as Monart (including Ysart paperweights), Gray-Stan and Stuart - none of them well known at street level - that will be under scrutiny at the auction next Thursday (2pm) and Friday (10.30am).

During his lifetime Parkington single-handedly pushed up prices for Scottish Monart glass of the Thirties - mostly colourful vases with abstract swirls and unusual textures - and the sale should push them up further. Jane Hay, head of Christie's South Ken's glass department, watched him bid what she thought were crazy prices for Monart in the Eighties.

In the sale, Ms Hay has estimated at only pounds 600-pounds 700 a lot of four miniature ovoid Monart vases, for just one of which he paid pounds 330 six years ago. And she has put a cautious pounds 300-pounds 400 on a Gray-Stan orange oval vase of about 1935 for which he bid pounds 1,430 in 1990. Comeuppance? Come- on, more likely.

Parkington's squirrelled away his trophies in his mansion flat in Kensington, which Ms Hay describes as "ceiling to floor with glass, glass spilling out of every cupboard, and with narrow, 16 inch pathways between the stacks of glass on the floor". When Parkington discovered Whitefriars glass in 1991, after prompting from Ms Hay, it "spread like a fungus throughout the flat" - he bought about 400 pieces in eight months.

Visitors were expected to put back his Ysart glass paperweights facing the same way, in their original ring of dust. These, with their embedded flowers, butterflies and fish, were another discovery of his. He would pay pounds 200-pounds 300 for a British Ysart. The 33 in the sale are estimated mostly pounds 100-pounds 200 or pounds 500-pounds 700. Watch them take off.

Another potential soaraway - Stevens and Williams "Transparent Cameo" vases of around 1900. They are acid-etched then hand-cut - the last flourish of old skills applied to new, rather than traditional, designs. The five in the sale are estimated pounds 100-pounds 150 to pounds 200-pounds 300.

Parkington had an eye for the Victorians' clever industrial processes. See whether bidders share his enthusiasm for the Apsley-Pellat "Crystallo- Ceramie" scent bottle of around 1830 containing a sulphide portrait of Queen Charlotte (pounds 600-pounds 1,000), the Varnish green candlesticks (about 1850) with silver-lined interiors (pounds 400-pounds 500), or the rare Webb "Alexandrite" specimen vase and tazza of about 1900 that is heat sensitive and changes from pink to turquoise when exposed to electric light (pounds 100-pounds 150).

Christie's South Kensington, 85 Old Brompton Road, London SW7 (0171- 581 7611). Catalogues pounds 12, with p&p pounds 12.80.