He showed artistic promise and spent 6 years in London with Daniel Fournier where he studied drawing and contributed some etchings to Fournier’s book A Treatise of the Theory and Practice of Perspective, wherein the Principles of that most Useful Art are Laid Down[4] Henderson was living with a relative of his mother, the silversmith William Cripps, in St James Street when Cripps died in 1766.

[1] Henderson’s imitation of David Garrick's Ode delivered at the Shakespeare Jubilee in Stratford upon Avon in 1769 was said to be hard to distinguish from the original recital.

Among other disappointments were rebuffs from George Colman, manager of the Covent Garden Theatre, and failure to interest the playwright Paul Hiffernan in casting him in one of his plays.

Henderson voice was deemed ‘woolly’,[1] but eventually David Garrick auditioned him and suggested he might be suitable for a provincial theatre, recommending him to John Palmer of Bath.

Known as "The Bath Roscius", Henderson performed from 1772 until 1778 in Palmer’s company, adding Lear, Othello, Posthumus, Shylock, King John, and Falstaff (in both Henry IV and The Merry Wives of Windsor) to his Shakespearean repertoire.

Despite his success in Bath and other provincial theatres Henderson’s ambition to act on the London stage was thwarted, in part by Garrick who may have feared a rival, until 1777.

He added Richard III, Shylock, Falstaff (in three plays), King John, Benedick, and Macbeth to his Shakespearean repertoire during the 1777–78 season, as well as playing Horatius in The Roman Father, Don John, Bayes, Brutus in The Roman Sacrifice (by William Shirley), Bobadil in Every Man in His Humour, Edgar Atheling in The Battle of Hastings, and Valentine in Love for Love.

He began the 1778–79 season at Drury Lane as Falstaff in The Merry Wives and continued there with much the same repertoire (adding Father Dominick in ‘The Spanish Fryar, Bireno in The Law of Lombardy and Beverley in Centlivre’s The Gamester).

Roles added to his now extensive repertoire included Gloster and Hastings in Jane Shore, Sir John Brute in ’’The Provok’d Wife’’, the title role in Vanburgh’s Aesop, Sforza in The Duke of Milan, Austin in The Count of Narbonne, Sir Giles Over-reach in A New Way to Pay Old Debts, Maskwell in The Double Dealer, Lusignan in Zara, Sciolto in The Fair Penitent, Evander in The Grecian Daughter, Pierre in Venice Preserv’d and Mr Ordeal in Fashionable Levities, a new play by Leonard McNally.

It was all profoundly intellectual like the character… Though a studious man, there was no discipline apparent in the art of Henderson; he moved and looked as humour or passion required".

[7] Although short of stature and sometimes awkward in his movements, Henderson’s character depiction was acclaimed and engravings of him in the roles of Hamlet, Iago and Macbeth became popular.

A procession of fifteen mourning coaches and other carriages accompanied his body to Westminster Abbey where he was interred close to the tomb of David Garrick and the memorial to Shakespeare.

[13] There were important collections within it, such as: Henderson married Jane, daughter of Thomas Figgins jr, a successful clothier of Chippenham, on 13 January 1779 at St Clement Danes in London.