LONDON, Dec 16 (Reuters) - Sci-fi series "Silo" will

return for two more seasons, with the third chapter already

shooting in the UK.

Apple ( AAPL ) CEO Tim Cook joined the series' star and executive

producer Rebecca Ferguson on the sprawling "Silo" set at

Hoddesdon Studios outside London to make the announcement.

"We feel great about it. We could not be more pleased. We're

already filming season three," Cook told Reuters in an interview

in the show's Silo 18 cafeteria.

"We get to walk around these environments again under new

circumstances, new threats," added Ferguson. "We're back on the

show and it's tense, it's wonderful and it's mysterious."

The dystopian drama is based on American author Hugh Howey's

"Silo" book trilogy and is set deep underground, where the last

remaining people have been sheltering for hundreds of years from

what they are told is a toxic environment on the surface of the

Earth.

Ferguson plays engineer Juliette, whose suspicions are

aroused when she seeks answers to a loved one's death, and she

becomes determined to expose the secrets of the silo. Season one

ended with Juliette stepping outside of Silo 18 and the second

season, currently streaming on Apple TV+, sees her world

upended.

The fourth season will conclude the series, the makers said.

Five years on from the launch of Apple TV+ in November 2019,

Cook said he considered the service to be "successful by any

measure".

"Like the rest of Apple ( AAPL ), we're about being the best, not

producing the most," said Cook.

"We're focusing on the best quality, with the best

storytellers, all original. We think 'Silo' is a fantastic

example of that and of course the UK is a great place for

storytellers and it's a place where people want to work, and so

we're doing a lot in the UK," he said.

New episodes of the 10-part "Silo" season two are released

weekly, with the show's finale premiering Jan. 17.

(Reporting by Hanna Rantala

Editing by Ros Russell)