Rhys Ifans has joined the cast of 'House of the Dragon'.

Rhys Ifans

Rhys Ifans

The 'Notting Hill' actor will portray Ser Otto Hightower, the loyal Hand of the King, in HBO's upcoming 'Game of Thrones' prequel, and he isn't the only new addition to the series.

Steve Toussaint will play nautical adventurer Lord Corlyn Velaryon, who is known as the Sea Snake, while Eve Best will be his wife, Princess Rhaenys Velaryon, a dragonrider dubbed 'The Queen Who Never Was' because she was passed over as heir to the throne because the realm favoured her male cousin, King Viserys Targaryen (Paddy Considine).

Rounding out the list of newcomers is Sonoya Mizuno, who will portray slave Mysaria who rises to become the most trusted and unexpected ally to Prince Daemon Targaryen (Matt Smith).

The 10-episode show - which is expected to launch in 2022 - will tell the story of House Targaryen and is set a few hundred years before the events depicted in 'Game of Thrones'.

Fans of writer George R.R. Martin will be aware that Viserys ruled Westeros around 100 years after Aegon's Conquest. His two children, Rhaenys and Aegon II, went on to fight a civil war over the throne that was famously known as the Dance of Dragons.

'House of the Dragon' is based on the author's companion book 'Fire & Blood' and HBO ordered it straight-to-series.

'Game of Thrones' regular Miguel Sapochnik is set to direct the pilot and additional episodes and he will act as showrunner alongside Ryan Condal, who created the upcoming show with Martin.

The show was announced after another spin-off, which was set to take place thousands of years prior to the events of the original series, was dropped by HBO after the pilot episode was shot.

The axed programme had cast Naomi Watts, Josh Whitehouse, Denise Gough, Jamie Campbell Bower, Sheila Atim, Ivanno Jeremiah, Georgie Henley, Alex Sharp, Toby Regbo, Miranda Richardson, Marquis Rodriquez, John Simm, Richard McCabe, and John Heffernan.