Lady Wortley Montagu famously introduced inoculation against smallpox from Turkey to Britain.

Soon after, Dr Dinsdale was contacted by the great improver Empress Catherine II of Russia to inoculate her, the first in her country, to encourage her subjects to follow.

On his arrival Catherine spoke with him, arranging for him to visit in secret at midnight. If she survived she promised a handsome reward . If not, she made arrangements to convey him secretly out of the empire before her death was announced.

The baron praised her noble nature and showed visitors many portraits of her, comparing her to a majestic lion; she could imitate perfectly a cock crowing or a hissing cat. He spoke of her wit, kindness and intellectual powers. She was well versed in literary and scientific names and used tact to serve friends or baffle their rivalry.