In 1935 Booysen founded a voluntary birth control clinic known as the Goswell Women's Welfare Centre in Finsbury, then a poor and overcrowded district of London.
[7] Booysen was one among a number of prominent women doctors who conducted medical trials to establish the efficacy and safety of contraceptive products.
[7] As Caroline Rusterholz has written:Booysen was tasked with gathering information on quinine, a drug first used to treat malaria but which had been used as a spermicidal jelly.
In The Lancet, Professor John A. Ryle wrote:The news of Dr. Cécile Booysen’s death will have brought grief and distress to all who knew her.
Among the many able women doctors in London, she belonged to a group and a generation which stands particularly high in my estimation, and established unobtrusively a position which will cause her to be long remembered and revered.
She was the organising secretary and inspiration of the Medical Peace Campaign in this country, and in her conduct of its affairs she must have expended a great deal of the energies of her later months.