The Doctor Who new-series opener features some terrifying villains – the alien Silence, to scare the kids, and Richard Nixon to creep out their folks

Forget about who might die for a moment – difficult I know, particularly if you like to buy your Christmas cards early – was the new Doctor Who any good? Answer: dead good.

In truth the opening episode of the two-parter took a while to warm up, but a fiendishly complicated plot – it is probably not a spoiler to suggest it involves time-travelling – required no end of exposition. But by the end of the first episode it had drawn gasps and applause in almost equal measure from a preview audience at London's Olympia on Monday.

Preaching to the converted in most part, no doubt, but this was scary stuff – almost as unnerving as those kids who kept asking for their mummy and the darkest series opener showrunner Steven Moffat could remember. And not a big-name celebrity guest star in sight.

Alien race the Silence had a particularly cute way of avoiding detection and owed plenty in their appearance to the bad guys from Predator. Terrifyingly, their chins are even bigger than the doctor's.

Setting it in 1960s America gave Moffat the chance for plenty of gags about new technology – "A videophone, whatever that is" – and lots of fun at the expense of White House incumbent, Richard Nixon.

"Each episode has the feel of a film," said star Matt Smith in a Q&A that followed the preview screening, and that was certainly true of the opening double-header. The Stateside locations – the Utah desert was real, the New York skyline slightly less so – gave it more of a Hollywood feel than a recreation ground near Cardiff that once stood in for the Statue of Liberty.

Moffat appeared a little grumpy at the launch, possibly as a result of the weight of expectation around the new series, possibly at the prospect of the assembled media giving away his big plot twist. Showrunner since last year's fifth series – the first to feature Smith in the lead role – Moffat said he put in jokes for the adults and scares for the kids, and this two-parter had plenty of both. Genuinely disconcerting at times, it felt positively Lynchian (that's David Lynch, not her out of Glee).

Assuming he isn't the one who gets bumped off – thereby making his thoughts redundant – Smith declined to confirm or deny whether he will stick around for a third series.

"I take it year by year and month by month," said the youngest Doctor to date. "We stop shooting in a month and I will sit down with Mr Moffat and see where we go from here. It's not a part I want to give up any time soon. Watch this space."

"I don't think it's too much of a poser to say we are going to continue with the Doctor as a regular character," offered Moffat. Steady on Steven, no spoilers!

But what chance the mysterious time traveller River Song, played by Alex Kingston, is in fact a future Doctor, and the first (you have probably noticed) female one? Kington reckoned not – shame – but then she doesn't write it.

But forget about regeneration, what one hack wanted to know was – did Kingston prefer slapping Smith or snogging him? "That's quite a difficult one," said Kingston.

"Thanks very much," replied Smith. But last word goes to president Nixon. "Will I be remembered?" asks the White House incumbent. Er, probably.