Is this Robert's father or his brother?
Pigot’s Directory of London, 1836
Leatherby John, tailor, 4 Michael's place, Brompton
Also this one's worth looking into:
Post Office Directory of London, 1843
Leatherby Thomas, tailor, 4 Michael's place, Brompton
But possibly a misprint because:
Post Office Directory of London, 1846
Leatherby John, tailor, 4 Michael's place, Brompton