Question: Who appeared in the London debut of a musical with music and lyrics by Stephen Sondheim?

Context paragraphs:
Saturday Night (musical): Saturday Night is a musical with music and lyrics by Stephen Sondheim, and the book by brothers Julius J. Epstein and Philip G. Epstein, based on their play, "Front Porch in Flatbush".  The musical was expected to open on Broadway in 1954-1955, but because of the lead producer's death, it was not produced.  Following a student production, it was staged at the Bridewell Theatre, London in 1997 and then in Chicago in 1999 and Off-Broadway in 2000.  The musical also ran in the West End in 2009.

Finishing the Hat: Finishing the Hat: Collected Lyrics (1954–1981) with Attendant Comments, Principles, Heresies, Grudges, Whines and Anecdotes is a book by American musical theatre composer and lyricist Stephen Sondheim.  The book contains Sondheim's lyrics from his first professionally staged show, "Saturday Night" (1954) through "West Side Story", "", "A Funny Thing Happened on the Way to the Forum", "Anyone Can Whistle", "Do I Hear a Waltz? ", "Company", "Follies", "A Little Night Music", "The Frogs", "Pacific Overtures", "", and ending with "Merrily We Roll Along" (1981), stopping just short of the Pulitzer Prize-winning "Sunday in the Park with George" (1984) which contains the song from which the title of the book is taken.

Marry Me a Little (musical): Marry Me a Little is a musical with lyrics and music by Stephen Sondheim, conceived by Craig Lucas and Norman René.  The revue sets songs cut from Sondheim's better-known musicals, as well as songs from his then-unproduced musical "Saturday Night" to a dialogue-free plot about the relationship between two lonely New York single people, who are in emotional conflict during an evening in their separate one-room apartments.  Despite knowing of the other's existence, they never get up the courage to talk to each other, though they imagine what such an encounter might be like.

Passion (musical): Passion is a one-act musical, with music and lyrics by Stephen Sondheim and a book by James Lapine.  The story was adapted from Ettore Scola's film "Passione d'Amore", itself adapted from the novel "Fosca" by Iginio Ugo Tarchetti.  Central themes include love, sex, obsession, illness, passion, beauty, power and manipulation.  "Passion" is notable for being one of the few projects that Stephen Sondheim himself conceived, along with "Sweeney Todd" and "Road Show".

Hot Spot (musical): Hot Spot is a musical with the book by Jack Weinstock and Willie Gilbert, lyrics by Martin Charnin, music by Mary Rodgers, and additional lyrics and music by Stephen Sondheim.  It had a brief run on Broadway in 1963.  The musical is a political satire.

The Sondheim Review: The Sondheim Review is a quarterly magazine published in Chicago, United States, since 1994 and, per its tagline, is "Dedicated to the work of the Musical Theatre's foremost composer and lyricist," Stephen Sondheim.  It is edited by Cincinnati theatre critic Rick Pender, and its editorial board includes theatre columnist John Olson and drama critic Eric Grode.  Sondheim himself has written occasional short items for the magazine, although he is not formally connected with the magazine in any way.

A Funny Thing Happened on the Way to the Forum: A Funny Thing Happened on the Way to the Forum is a musical with music and lyrics by Stephen Sondheim and book by Burt Shevelove and Larry Gelbart.

Sondheim on Sondheim: Sondheim on Sondheim is a musical revue consisting of music and lyrics written by Stephen Sondheim for his many shows.  It is conceived and directed by James Lapine.  The revue had a limited run on Broadway in 2010.

Ben Wright (American actor): Ben Wright (born September 3, 1969) is best known for originating the role of "Jack" in the Tony Award-winning musical "Into the Woods".  Wright's professional acting career started with George C. Wolfe's Off-Broadway production of "Paradise" at Playwrights Horizons.  He then went on to originate leading roles on Broadway in Stephen Sondheim's "Into The Woods" and the Tony nominated "State Fair", for which he received a Drama Desk Nomination.  He also created the role of Nanki Poo in Hot Mikado at the Ford's Theater in Washington, D.C. He has worked extensively with some of Broadway’s greatest talents, including Stephen Sondheim, James Lapine, Bernadette Peters, James Hammerstein, Paul Gemignani and Joanna Gleason.  Wright's feature film credits include the Academy Award winning "Born on the Fourth of July" with Tom Cruise as well as Penny Marshall's "Renaissance Man" with Danny DeVito.  Wright's television credits include starring opposite Judd Nelson in NBC's "" and the ABC drama series "Capital News" with Lloyd Bridges and Helen Slater.  Wright has performed at the Tony Awards two times and can be heard on several albums, including the original cast recording of State Fair and the Grammy Award winning recording of "Into the Woods".

Isla Blair: Isla Blair (born 29 September 1944) is an Anglo-Scottish actress.  She made her first stage appearance in 1963 as Philia in the London debut of "A Funny Thing Happened on the Way to the Forum".

Supporting paragraphs: Isla Blair A Funny Thing Happened on the Way to the Forum
Answer: Isla Blair