Planché's career as a playwright began, as already mentioned, in 1818 when "Amoroso, King of Little Britain", a play he had written for an amateur performance at a private theatre, was seen by John Pritt Harley and subsequently performed at Drury Lane. The play was a success and Harley, along with Stephen Kemble and Robert William Elliston, encouraged Planché to take up play-writing full-time. Planché did so; his next play to be performed was a pantomime at Christmas of that same year. A further six of his plays were performed in 1819, the same number in 1820, and eleven in 1821, most of these at the Adelphi Theatre, but also including some at the Lyceum, the Olympic and Sadler's Wells. Planché's early works were "generally unremarkable", one exception in this period being "The Vampire, or, The Bride of the Isles", produced at the Lyceum in August 1820, an adaptation of Charles Nodier's "Le Vampire" (this was a dramatisation of John Polidori's novel "The Vampyre"). The play featured the innovative "vampire trap", a trapdoor in the stage which allowed an actor to disappear (or appear) almost instantly. "Kenilworth Castle, or, the Days of Queen Bess", produced 8 February 1821, was also very successful. Planché wrote a total of 176 plays.