ITV has defended killing off one of Downton Abbey's main characters in the Christmas Day special.

Warning: spoiler alert!

Fans saw Matthew Crawley (Dan Stevens) die in a car crash just after his wife Lady Mary (Michelle Dockery) had given birth to their first child.

In a statement, ITV said that because Stevens had decided not to renew his contract after three seasons, it was decided that killing his character off was the best option.

The statement said: "Over the last three years, audiences across the world have been captivated by the ups and downs of Mary and Matthew's relationship, culminating in their wedding.

"Fans have enjoyed what has become a solid and loving marriage.

"It is for this reason that the producers decided Matthew and Mary could not simply be estranged or parted, resulting in his untimely and tragic death at the end of the Christmas episode.

"In the next series, alongside all the usual drama, comedy and romance involving the much-loved cast of characters, viewers will see Mary adjusting to her life and attempting to move on without the man she loved."

The fourth series of Downton Abbey will begin filming in February.