in 1779, and, having taken holy orders, was chosen in 1781 fellow and conduct (or chaplain) of King's College, Cambridge.
[1][2] In 1783 Professor Thomas Martyn (1735–1825) gave Relhan all the manuscript notes he had made on Cambridge plants since the publication of his Plantae Cantabrigienses in 1763.
With this assistance Relhan published his chief work, the Flora Cantabrigiensis in 1785, describing several new plants and including seven plates engraved by James Sowerby.
His name was commemorated by L'Heritier in a genus, Relhania, comprising a few species of South African Composite.
There is a watercolor painted by him of the Barnwell Leper Chapel, the oldest complete building in Cambridge.