Arthur Seymour Sullivan and William Schwenk Gilbert first met in 1869, introduced by the composer Frederic Clay. Both were already established masters of their own respective arts. But it was John Hollingshead, manager of the Gaiety Theatre, who first commissioned them to write together for his 1871 winter season and thus inaugurated arguably the most successful partnership in the history of British theatre.

Trial By Jury opened on 25 March 1875 alongside and was an immediate success. After transferring to the Opéra Comique Theatre, off the Strand, early in 1876 and thence to the Royal Strand Theatre in 1877, Trial by Jury ran for around 300 performances.

Mostly G&S was formed in 2009 to create a small group devoted to the works of Gilbert and Sullivan but presented in a concert style with the emphasis on the music and an authentic adherence to the original scores.

Jeff Trim has performed more than sixty principal roles in works as diverse as The Marriage of Figaro, Macbeth, The Elixir of Love, A Masked Ball and Turandot.

Jenny Spence’s childhood treat was being taken to see G&S at Sadler's Wells every Christmas. She was rather older when she started performing G&S with Mostly G&S, starting out in the chorus for Yeomen of the Guard.

Simon King is an experienced accompanist, having played for several groups in theReading area. He has also been musical director for shows with Woodley Light Operatic Society and as a former school music teacher has directed many musicals.

Andrew Evans, John Painter, Fee Trim and Edwin Trout are also members of Mostly G&S.