Sebastian Theodore Kemble Croft was born in Oxford to John Croft, a businessman, and Doulla Croft, an executive at Facebook. He attended the Dragon School in Oxford and it was from there that he was cast in his first professional production at the age of seven in the UK tour of Chitty Chitty Bang Bang. His first West End stage appearance the following year was in the Sam Mendes production of Oliver at the Theatre Royal Drury Lane. Sebastian then played Gavroche in Les Misérables in 2011, along side Matt Lucas and Alfie Boe. For the next eighteen months he toured the UK in the title role of Oliver for Cameron Mackintosh. He then went on to join the Royal Shakespeare Company in the award winning West End production of Matilda, playing the role of Tommy. In 2014 his vocals were used during the Donmar Warehouse production of Coriolanus with Tom Hiddleston; and Sebastian's final musical theatre production was in the lead role of Adrian Mole at the Leicester Curve for the world premier of The Secret Diary of Adrian Mole The Musical.
At Christmas 2014 Sebastian appeared in the video to Michael Bublé and Idina Menzel's "Baby It's Cold Outside", which reached number one in the US billboard charts.
In 2015 Sebastian was signed by Curtis Brown and has since filmed Season Three of Penny Dreadful (2014) for Sky Atlantic and Showtime; he will appear in Houdini and Doyle (2016) for ITV and Fox; he is currently (November 2015) making Music, War and Love (2016), a feature film being shot on location in Poland, alongside Stellan Skarsgård and Adelaide Clemens; and he is in pre-production for the feature film The Hippopotamus by Stephen Fry.
