It's cost the earth - now Terra Nova needs an audience

After production delays, a flooded set, rising budgets and the firing – then rehiring – of its entire writing team, Steven Spielberg's sci-fi drama series Terra Nova has finally arrived. Almost.

Fox yesterday unveiled the opening episode of the most expensive television series in history, billed as a $70m (£43m) CGI-packed mix of Avatar and Jurassic Park. Each minute of the series has cost an estimated £200,000 to get to the small screen.

Mobile phones were confiscated from those who attended an exclusive screening at the Fox headquarters in central London yesterday, and embargo forms were signed by the first to see the show, which is co-produced by Spielberg.

But barely had Spielberg's trademark dinosaurs begun chomping their way through the cast, when the words flashed up – To Be Continued. The most expensive pilot episode yet, at $20m and due to be screened in May, is still not finished.

Fox, part of Rupert Murdoch's News Corporation, said it had made a "big bet" with Terra Nova, due to launch in prime time in the United States and on Sky 1 HD in the UK, later this month.

The 13-part series follows the Shannon family who are sent back in time 85 million years from the year 2149 to prehistoric earth to save the human race from extinction.

The cast is led by Irish actor Jason O'Mara and Shelley Conn, previously seen in Mistresses, who is allowed to retain her English accent. Conn, 34, has a screen daughter, played by Naomi Scott, 18, a rising star from Hounslow, who talks pure American.

Terra Nova's production has been troubled. Producer David Fury left due to "creative differences". The entire writing team was fired to save money as costs begin to soar – and then rehired. The Australian set was hit by record flooding.

Hollywood screenwriters, on reported salaries of $200,000 a week, have been drafted in to give more "heart" to the story. The opening episode has already been re-edited to upgrade the family storyline at the expense of the spectacular dinosaur action.

Produced by Jon Cassar, the man responsible for the breakneck-paced series 24, the opening episode of the series owes a clear debt to Avatar, with its "pioneer colony must save the planet" storyline. Stephen Lang, who played the crazy Colonel Quaritch in Avatar is the leader of the Terra Nova colony.

Fox hopes to make its money back on international sales, DVDs, and downloads. Kevin Reilly, entertainment president at Fox, said: "The start-up cost for the series is definitely on the high end, but we are in the big bet business." Even the Queensland rains which held up production were a positive. "That created some great atmospherics."