[1] He was born on 17 December 1748 in Salisbury Street, Strand, London, to Peter and Ann Wewitzer; his parents were involved in the theatre, and his father was Swiss or Norwegian.

Among his parts at Covent Garden were Filch in The Beggar's Opera, Champignon in The Reprisal by Tobias Smollett, Jerry Sneak in The Mayor of Garratt by Samuel Foote, Simon Pure in A Bold Stroke for a Wife by Susanna Centlivre, Dr.

Pinch in The Comedy of Errors, Coromandel (an original part) in Frederick Pilon's Liverpool Prize, 22 February 1779, and Dr. Caius in The Merry Wives of Windsor.

In Omar, or a Trip round the World, by O'Keeffe, with music by William Shield, produced at Covent Garden on 20 December 1785, Wewitzer delivered an effective harangue in what purported to be the language of a Polynesian chief.

[2] On 8 July 1780 Wewitzer appeared at the Haymarket Theatre as Fripon in Miles Peter Andrews's comic opera Fire and Water, then first produced.

On his failure and imprisonment in 1789 he gave the management to Wewitzer, who severed his connection with Covent Garden and sought to make the Royalty a popular house, on the lines Sadler's Wells.

[2] Wewitzer played a part in arranging the marriage in 1815 of the actress Harriot Mellon to Thomas Coutts, who died in 1822 at age 86; and he was for a short time a member of her household.

An account in Mrs. Cornwell Baron Wilson's memoirs of Harriot suggests that Wewitzer was either a family friend, or knew her from the time when she joined the Drury Lane Theatre, which was 1794–5.

[2][8] A pamphlet Mr. Percy Wyndham's Strictures on an Impostor was written in alignment with Wewitzer's financial interests, and taxed her with falsehood and ingratitude.

[12] On the other hand, Anthony (John Williams) wrote of Wewitzer suggesting his acting range was limited, but his performances masterly:[13] Yet his Caius and clowns we may see and admire, And his Bellair, like glass, is engendered by fire.