Mantell was born in Scotland and first appeared on stage in Belfast, Northern Ireland; for a time he used the stage name Robert Hudson, but he reassumed his name Mantell after he joined the company of Helena Modjeska in 1878 and came to the United States. He returned to England, but he met with little sucess and returned to the United States permanently, where for years he toured with his own company. He was not particularly popular in New York City, so he toured other cities in the United States. He was an indefatigable worker--something of a war-horse, in fact--and he was constantly on the road with his troupe. One way to keep a leading actress with this kind of schedule was to marry her, which Mantell did four times.

Although he was a respected Shakespearean actor on the road, it is hard to judge just how good he was, his having failed to excite the critics or the public in either London or New York.

A story in The Methuen Book of Shakespeare Anecdotes helps explain the ill-fortune that plagued the man's productions: