Physician, philanthropist, abolitionist and entomologist. Born British Virgin Islands into a Quaker family. Aged 6 was sent to England to be educated. Came to London in 1766 to train at St Thomas' Hospital. Founder of the Medical Society of London of which he was president on and off, 1775 - 1815.
He signed his prescriptions “I” which prompted this rhyme (of which there are some variant versions):
When patients ill, they comes to I,
I physicks, bleeds and sweats ‘em:
Sometimes they live, sometimes they die,
What’s that to I? I Lettsom.
A noted abolitionist, on the death of his father he returned to the Virgin Islands where he freed the slaves he had inherited. But later, his son, through a wealthy marriage back in the Virgin Islands, brought slaves back into the family and Lettsom inherited them shortly before he died. Thus he died with 1,000 slaves in his estate. He had some explaining to do at the pearly gates.