'The Last Kingdom' Star Adrian Schiller Dead at 60

English actor Adrian Schiller has died ... his longtime talent agency, Scott Marshall Partners, confirmed Thursday.

In a statement released to People ... Adrian's team shared the actor passed away on Wednesday, describing his death as "sudden and unexpected."

The agency added, "He has died far too soon, and we, his family and close friends are devastated by the loss."

They didn't provide any details as far as Adrian's cause of death.

However, his sister Ginny posted that he had died while at his home, and added ... "He had so many very dear friends - sorry to those of you who are learning about this here. We will say more about funeral and/or memorial plans in due course."

Adrian was best known for starring in the British period drama, "Victoria," in which he played a servant to Jenna Coleman's Queen Victoria. He also had a small but important role in the 2017 live-action remake of "Beauty and the Beast," where he played Monsieur D'Arque.

Between 2018 and 2022, Adrian was a main cast member for "The Last Kingdom," playing Ealdorman Aethelhelm in the historical drama.

Prior to his death, Adrian -- an accomplished stage performer -- was starring in the National Theatre's touring production of "The Lehman Trilogy."

National Theatre director Rufus Norris says, "We are deeply saddened and shocked to have lost our company member and friend."

Adrian was 60.