A RENOWNED horticulturalist who developed the world famous Sissinghurst Castle gardens in Kent died from a lung cancer caused by asbestos exposure, an inquest heard this week.

But how award winning gardener Pamela Schwerdt came to be exposed to the deadly mineral remained a mystery after her inquest in Gloucester.

Gloucestershire coroner Alan Crickmore heard that in the late 1940s and through most of the 1950s she stoked boilers at the Waterperry horticultural school near Oxford.

But there was no other evidence of asbestos exposure either in her working or social life, said the coroner. He recorded an open verdict.

Miss Schwerdt, who lived at Manor Farm, Condicote near Stow, died aged 78 of malignant mesothelioma on September 11 last year. She was diagnosed with the disease in 2008.

Analysis of her lung tissues revealed 57,047 mineral fibres per gram of dry lung tissue - a “moderate” accumulation of fibres consistent with causing mesothelioma.

Coroner Mr Crickmore said he was satisfied that absestos exposure led to Miss Scwerdt's death, but the question remained on how she came to be exposed.

Miss Schwerdt was joint head gardener for 31 years, with Sibylle Kreutzberger, at the garden at Sissinghurst Castle, created by Sir Harold Nicolson and his wife Vita Sackville-West.

She retired from Sissinghurst in 1990. She and Kreutzberger then started a new and smaller garden in Gloucestershire.

Miss Schwerdt was awarded the RHS Associate of Honour in 1980 and appointed MBE in 1990.

In 1992 she was was co-recipient, with Kreutzberger, of the third International Carlo Scarpa Prize for Gardens awarded by the Fondazione Benetton. In 2006 she was awarded the Victoria Medal of Honour by the RHS.