Who is Mark Gatiss's character the Captain in the Doctor Who Christmas special?

Brigadier Alistair Gordon Lethbridge-Stewart, played by the late Nicholas Courtney and better known simply as the Brigadier (or even the Brig, if you're feeling particularly lazy) was one of the founders of UNIT – the United Nations Intelligence Taskforce (later the Unified Intelligence Taskforce) which defended Earth from alien threats – and a regular ally of the Doctor from his second to seventh incarnations.

New Who fans will be more familiar with Jemma Redgrave's Kate Stewart, the Brigadier's daughter and UNIT's chief science officer, but will also remember a recent appearance from the Brig in his resurrected form as a Cyberman who rebelled against his creator Missy to save Kate's life.

But just where does Gatiss's Captain Lethbridge-Stewart fit in? Well during a Q&A after the press screening of Twice Upon a Time, Gatiss told us he was the Brigadier's grandfather, and therefore Kate's great-grandfather, and since we meet the Captain at Christmas 1914 when he already has children of his own, that adds up.

"Amongst the many gifts Doctor Who has given me, to end up being the Brigadier’s grandfather, I couldn’t have imagined anything more brilliant," said Gatiss.

And he revealed that he hadn't realised exactly who his character was until he read the script.

And what happened when he came across those words, Captain Archibald Hamish Lethbridge-Stewart?

"Well I started crying…"

Chances are he won't be the only one.