Most evidence for Leland's life and career comes from his own writings, especially his poetry. He was born in London on 13 September, most probably in about 1503, and had an older brother, also named John. Having lost both his parents at an early age, he and his brother were raised by Thomas Myles. Leland was educated at St Paul's School, London, under its first headmaster, William Lily. It was here that he already met some of his future benefactors, notably William Paget.