‘Game of Thrones’ continues to add to its cast as actor Richard E. Grant, who appeared in Downton Abbey in its fifth season, has reportedly signed on to the hit HBO series ahead of the upcoming installment.

Although there have been no details with regards to the character that he will be playing in season six, community fan-site Watchers On The Wall reported that ‘Game of Thrones’ has been added to the actor’s agency CV, more recently than his newest projects ‘Dig’ and ‘Jekyll and Hyde.’

With the HBO series catching up with George R.R. Martin’s novels, online speculations have been claiming that the ‘Downton Abbey’ actor could take on the role of Citadel archmaster Maester Marwyn or Lord Paxter Redwayne. Both characters have been featured in the book series but have yet to be portrayed in the TV program.

House Greyjoy and House Tarly will also be of great importance when the sixth season comes, hence the possibility that Grant could play a member of either of such families.

Meanwhile, Martin has already faced the possibility that HBO could hasten the pace of the hit show, which means that the network could already put forward the program’s concluding episodes even before the last book un his ‘ASOIAF’ series is released.

In an interview with GeekWire, the award-winning author opened up about his thoughts on the TV version possibly coming to a conclusion before his books.

"Anything is possible," Martin said as he acknowledged the fact that the hit HBO fantasy drama is moving like a "jet locomotive." "They're writing 60-page scripts, I'm writing 1,500-page novels," he said. "So who the hell knows?"

Martin also admitted that he had once been worried about the TV adaptation coming to a close first before his own book series, but later on realized that worrying would not put off such possibility.

"Worrying about it isn't going to change it one way or another. I still sit down at the typewriter, and I have to write the next scene and the next sentence,” he shared. “I'm just going to tell my story, and they're telling their story and adapting my books, and we shall see."

In addition, ‘Game of Thrones’ showrunners David Benioff and Dan Weiss previously shared their sentiments on the HBO program ending sooner than their published counterparts.

"Luckily, we've been talking about [the series outpacing the books] with George for a long time, ever since we saw this could happen, and we know where things are heading," Benioff explained. "And so we'll eventually, basically, meet up at pretty much the same place where George is going; there might be a few deviations along the route, but we're heading towards the same destination."

‘Game of Thrones’ season six is expected to air in April 2016 on HBO.