This was a wise and thoughtful opening gambit from Moffat, and from the wonderful Capaldi – if you can utterly disregard the demented plot. Granted, this might be like saying "apart from that, 6 August was a typically pleasant day in Hiroshima", but the underlying, and cleverer, theme was of age, and ageing, and looks, and perception, very nicely summed up when Clara (Jenna Colman, in a performance of great nuance if you can forget that last faux-Scots diphthong) asks the pretty lesbian lizard-lady, "When did you suddenly stop wearing that veil?" "When you stopped seeing it," comes the reply.

The whole thing is daft, some say. Certainly the plots, much of the bangy noise, and all of the hype. But some tremendous subtleties emerge. The restaurant scenes were genuinely scary. And Commander Strax, that cross between R2D2 and a pepperoni Wayne Rooney, for instance taught last night's teenagers a great difference by saying "it is to be hoped" (correct) rather than the over-misused "hopefully".

Euan Ferguson, The Observer

In the spirit of empathy, you might have wondered what younger viewers – if children still watch Doctor Who – were supposed to make of such existential hand-wringing while they were waiting for the fighting to start. To be fair, there was a smattering of comedy to enjoy as Clara exchanged amusing cultural misunderstandings with some of the Doctor's old plasticky alien acquaintances, but the jeopardy – clockwork zombie androids harvesting body parts – was a long time coming and lazily derivative in form (knowing acknowledgements to Burke and Hare and Sweeney Todd didn't make it less so). The excitement was over before Capaldi had the chance to stamp his personality on things.

Phil Hogan, The Observer

Peter Capaldi’s 12th Doctor has probably been the most fiercely anticipated new leading man in the show’s history. And in the end he was … probably exactly how you would imagine Peter Capaldi playing the Doctor to be. Not the Malcolm Tucker clone that Tumblr had so much fun anticipating, but far from an easy sell, either. We saw, at the end, the vulnerability underneath, but it took a bloody long time to get there. And when the 11th Doctor turned up at the end to reassure Clara that this was the same man (surprise! And well done if you managed to avoid that spoiler), he was pretty much doing the same for the audience.

Deep Breath was a gothic period drama, true to promises of a show with a grittier tone and longer, more grounded scenes. In many ways, it was surprisingly low-key for a series opener. In reality, it maybe could have done with being shaved down to an hour.

It’s a measure of Doctor Who’s madness that our familiar territory is the Victorian household of a lizard detective, her ninja housemaid wife and their Sontaran butler, but here we are, and it’s lovely and familiar to have them back. Neve McIntosh as Madame Vastra is emerging as a true star of the show, and she gets fleshed out, with her blunt condemnation of Clara’s attitude and her lustful manipulation of Jenny. Here is an inter-species lesbian couple in the 19th century that you can actually believe in.

Dan Martin, The Guardian

Writer Steven Moffat’s smart dialogue got the jump on viewers by second-guessing how they would be commenting from the sofa: there were references to Capaldi being grey, wrinkly and Scottish (like Moffat himself). His first word was “Shush!”, as if silencing potential naysayers. Capaldi signals a conscious break from the Doctor’s boyish recent incarnations. A blend of Doctor Doolittle and Sherlock Holmes, he crackled with fierce intelligence and nervous energy. Whether riding a horse in his pyjamas or dismissing Earth as “planet of the pudding brains”, he was a class act. His unpredictable air added dramatic tension. Twice he abandoned Clara and it was uncertain whether he would come back for her.

Along with its new leading man, the show had taken the opportunity to spruce up in other aspects. There was a new credits sequence (with the usual time tunnel being replaced by rather literal clocks and cogs), a tweaked, squeaky theme tune and a redecorated Tardis (an industrial look which rather complemented Capaldi’s all-black outfit). The tone seemed different, too, quieter and more thoughtful – less about running down corridors holding hands, more about self-discovery and redemption.

Michael Hogan, Telegraph

Look, I know that I’m the voice of bitter old fans who think New Who was rubbish from conception, but I’ve stuck with the show and I want it to succeed. I also want it to be daring in more than just a visual or political way. I want it to be sophisticated, fun science fiction that opens kids’ minds to intellectual possibility. Maybe this new series will move in that direction, maybe not. But I will still be watching it. If only to find out what that crazy lady with the umbrella is up to.

Tim Stanley, Telegraph

‘Deep Breath’ is fun enough but is unlikely to become an instant classic in the same way as Smith’s introduction in ‘The Eleventh Hour’. Ben Wheatley’s superb direction keeps things creepy and adult. The special effects and cinematography are dazzling.

Meanwhile Moffat’s script is suitably darker and more mature to match the new Doctor, yet the Time Lord's dialogue is side-splittingly funny to balance the darkness. Within the story he even addresses everything from Scottish independence, the Doctor's age and Clara's relationship with the previous incarnation, which is an impressive feat in itself.

Neela Debnath, Independent

Capaldi plays the tartan time traveller as a serious thinker, an almost troubled being, with a burden. An independent soul, he is not ?nding his way in the world – he has already been there. In short, the new Doctor is one of us; older, kindly, grumpy at times, and with regrets. “I’ve made mistakes,” he says solemnly.

Once he gets over his post-traumatic regeneration disorder, this worldly Doctor could become a classic but do not expect the scarf to make a return. He may be an avuncular Doctor in a frock coat but he will not be reaching for the pipe and slippers.

David Stephenson, Express

Deep Breath is simultaneously familiar and yet unfamiliar. It’s a familiar ‘new Doctor’ episode which touches on the after-effects of regeneration. Steven Moffat’s clockwork droids from The Girl in the Fireplace return. And we’re reunited with the Paternoster Gang of Vastra, Jenny and Strax, who help uncover the droids’ murderous attempts to repair their spacecraft and reach the promised land. At the same time, however, everything is different. The Doctor himself certainly is, with both he and Clara struggling to come to terms with his new appearance and personality.

This is unmistakably a new style of story for a new Doctor. While there’s plenty of Moffat’s rapid-fire wordplay and humour, we’re no longer constantly hurtling from one hyperactive setpiece to the next. Instead the characters are allowed to carry the story. Will this continue when we return to standard length episodes? We’ll have to see.

Tim Liew, Metro

Not much is natural in Doctor Who. But Peter Capaldi’s debut as The Doctor was so astute and assured it quickly confirmed that he has the type of wily charisma that makes it a role he was born to play. In fact Capaldi was so confident about his selection as only the twelfth actor to portray one of television’s great icons that he even let himself be upstaged on his big night – not once but twice.

Capaldi’s low-key start was a welcome change to the zany antics of both Matt Smith and David Tennant when they burst into the show and which set the tone for The Doctor’s previous two incarnations. It was always hard to shake the suspicion that the way Smith and Tennant played The Doctor with such ostentatious gusto was more about making themselves popular than just playing him. Their grinning idiocy didn’t leave much room for The Doctor’s fabled gravitas, borne of 2000 years time travel. In Capaldi’s capable hands this will return, while The Doctor’s problems adjusting to his regeneration were less madcap and had more pathos.

All in all, it was an impressive, entertaining start for the new era, which will surely see Capaldi coming more and more to the fore.

Jim Shelley, Daily Mail

It's almost impossible to wade into Doctor Who. You can't just settle on the sofa and switch it on carelessly. If you're a novice you need to prepare. You must study the history and the recurring characters. It's like trying to understand the Second World War: you need to go back and understand the First, and to understand the First you need to go back further still and try to understand Imperialism and the intricacies of the European balance of power…it's exhausting.

You can't just turn up, fresh-faced and keen, hoping to innocently enjoy some Saturday night TV. There is just too much history and backstory with Doctor Who and it feels like it's groaning under the weight of its own continuity as well as under the demands of its fans.
Julie McDowall, Herald Scotland

I never had any doubt that Peter Capaldi would be brilliant. He is. On the evidence of Deep Breath, he’s the Doctor I’ve longed for since the series came back in 2005 – quite frankly, since 1981 when Tom Baker’s Doctor plunged to his demise. For many I’ve spoken to, he’s the perfect choice. They’re already convinced. But, in Deep Breath, the programme itself seems overly anxious that its now global audience won’t take to an older, craggier Time Lord. It is willing those millions attuned to, nay moistened by, the geeky good looks of Messrs Tennant and Smith to have faith in Capaldi.

Patrick Mulkern, Radio Times

As a standalone episode of Doctor Who, it had almost everything a fan can hope for. But more importantly, and more interestingly, it set us up for a turbulent series, which we now know culminates in the departure of Clara Oswald... although we don’t yet know how.

One certainty remains. Whether you love or hate Steven Moffat-written episodes, and in spite of Moffat’s love for neatly packaged, filmic individual episodes, he remains the master of the story arc.

If you watched Deep Breath and you don’t want to watch the rest of series 8, then there truly is something wrong with you (indeed, you may need help from a Doctor).
Richard Beech, Mirror

Never was it clearer that this was a regeneration, not a rejuvenation, in Doctor Who’s most hallowed traditions, that much will be demanded of its youthful audience. But, if the challenges may be great, so too will be the rewards. Judging by Peter Capaldi’s debut episode, the Tardis is, once again, in very safe hands.

Caroline Frost, Huffington Post

Capaldi’s incarnation of the sci-fi icon is a more mature, no-nonsense expression of Who-ishness, lacking the rubbery physicality of Smith but remaining as quick-witted and free spirited as ever. He’s a throwback to darker tones of the first few Whos—intentionally, per the behind-the-scenes feature that accompanied the episode. That modality is captured by the look he’s chosen for himself, a fitted long black coat streaked with crimson on the inside, suggesting power, danger, and a little whimsy. He’s a top hat and longer tails away from resembling an old-school stage magician. This is not another romantic, “boyfriend” imagining of Doctor Who, and it isn’t another reckless, rogue/borderline anti-hero version of the franchise, either. At least, not yet. “I’ve made a lot of mistakes,” he tells companion Clara (Jenna Coleman). “It’s time I did something about that.” We’ll see how that goes.

As bold and refreshing as this out-with-the-old, in-with-the-older regeneration promises to be, I resented the manipulative ways in which the premiere demanded we roll with things. The new era of Doctor Who should do the hard work of earning our affection and loyalty—not vice versa.

Jeff Jenson, Entertainment Weekly