She was described by playwright Simon Farquhar in 2014 as being "one of television's finest period storytellers",[1] and in 2017 fellow dramatist Ian Curteis referred to her as "the Miss Marple of British playwriting".

[2] She started reading English at University College London during the Second World War and took a two-year hiatus from her course to volunteer for the Women's Auxiliary Air Force.

[2] While Sisson was working as a drama critic, Richard Burton's performance as Prince Hal in Henry V led her to take an interest in the affair between King Henry V's widow Catherine of Valois and Sir Owen Tudor, inspiring her to write the play The Queen and the Welshman in iambic pentameter.

The play was performed at the Edinburgh Festival Fringe with a cast including Edward Woodward as Owen Tudor and Frank Finlay as the Gaoler.

[10] William Aubrey Darlington, drama critic of The Daily Telegraph, praised Sisson's "keen nose for stories that are both true to actuality and to stage affect.

When John Wiles adapted The Queen and the Welshman for this version, Sisson sat next to him and asked questions about the art of writing television screenplays.

[citation needed] Sisson's other plays include A Ghost on Tiptoe, co-written with the actor Robert Morley, which had a run at the Savoy Theatre in 1974.

[2] She contributed scripts to the television series The Six Wives of Henry VIII (1970), Elizabeth R (1971), Upstairs, Downstairs (1972–75), The Duchess of Duke Street (1976–77),[7] and A Dorothy L. Sayers Mystery (1987).

She wrote screenplays for a few projects for British animation studio Cosgrove Hall in the late 1970s and early 1980s, she completed adaptations of The Talking Parcel (1978), Robert Browning's poem of The Pied Piper of Hamelin (1980) and The Wind in the Willows.