Bodyguard, episode 4: now the sex has gone, it's all killer twists and conspiracies - but who can be trusted?

The hit political thriller entered the home stretch with one shock death, almost a second and a deepening conspiracy. 

In the week that Bodyguard was confirmed as British TV's biggest new drama in more than a decade, with more than 10m tuning in, could it maintain momentum? 

Here’s all the talking points from episode four…

Home Secretary is dead… Or is she?

RIP, Julia Montague MP. For the first half of this rug-pulling episode, it never really occurred to me that the female lead would perish. Sure, the home secretary was in critical condition after episode three's bomb attack but the last we saw of Keeley Hawes' character, she seemed to be still breathing. 

On the 25-minute mark, though, came the shock revelation: Montague succumbed to her injuries. The second assassination attempt had been successful. Hands up if you saw that coming. Not you, Jed Mercurio.

Line of Duty creator Mercurio is by no means averse to shockingly killing off major characters mid-series. In fact, he takes a perverse delight in it. Lennie James, Jessica Raine, Daniel Mays and Jason Watkins were all billed as big stars across the cop corruption drama's four series, but all met head-spinningly premature ends – as did Gina McKee and Keeley Hawes, who both happen to be Bodyguard cast members too. 

This might be clutching at narrative straws, but could Montague's death even be faked to fool the terrorists? We didn’t see the ice queen-cum-saucepot fight for her life, lose the battle or glimpse her corpse. Would bringing her back from the grave be a twist too far?

Budd's suicide bid had a killer twist

So far in the series, actor Richard Madden – Games of Thrones’ former King of the North – has basically been a sexy Action Man with swivelling eagle eyes. 

As war veteran-turned-supercop Sgt David Budd, he was heroic on the train and during the bullet-peppered assassination attempt. He has brooded, shouted, chivalrously whipped off his shirt, flexed his jaw with post-traumatic angst and stared moodily into space over aggressively swigged beers in his darkened apartment. 

Now, though, Madden got to do some rather more nuanced acting. He went from shell-shocked in the wake of the explosion to heartbroken as he wept over Montague's death – both grieving for his lover and feeling guilt over "the principal" dying on his watch. 

Even his suicide bid was a rollercoaster scene, as Budd held the gun to his head, couldn't go through with it, shouted in despair, then regrouped and pulled the trigger. There was a bang and a spray of blood. Budd didn't answer his door when worried wife Vicky (Sophie Rundle) knocked and called. For a while back there, it looked like Mercurio had killed off both his lead characters within the space of four minutes – and even for this master of surprise, that would have been going some. Then came the twist. 

The bullets had been mysteriously switched for blanks. Budd had a painful looking head wound and a ruptured eardrum but nothing more. Don a baseball cap, keep calm and carry on. Phew. We're not sure we could have coped with a double death. 

Is prime suspect Tahir a red herring?

Lurking in the wings as Montague made a speech about her new counter-terrorism bill "RIPA 18", aide Tahir Mahmood (Shubham Saraf) was killed instantly. Was that because he detonated the device and the blast originated from his mysterious silver briefcase?

Circumstantial evidence certainly seemed to point that way – although, as I mentioned last week, it appeared to me that the explosion came from the front left of the stage, rather than further back. 

Despite his lack of terrorist links and thorough vetting, the police seemed eager to pin the murders on PR advisor Tahir and were soon calling him a "presumptive suicide bomber". We're sure his ethnic background had nothing to do with that. Ahem.

Was there a bomb in the briefcase that Budd overlooked, be it accidentally or deliberately? Or was it, as he insisted, just Home Office documents and background research material relevant to Montague's speech? As Mercurio tweeted last week: "We thought long and hard whether to show you what was in the briefcase. And decided not to." Oh, the big tease. 

Interrogation scenes came in threes

Line of Duty is renowned for its trademark interrogation scenes: tense cat-and-mouse grillings in grey meeting rooms which unfurl slowly yet remain fiendishly gripping. Here we were treated to three such sequences. 

Over seven minutes, professionally suspicious SO15 counter-terror cops DCI Deepak Sharma (Ash Tandon) and DS Louise Rayburn (Nina Toussaint-White) probed Budd as a person of interest, After all, since he's been Montague's bodyguard, two attempts had been made on her life. "I don't believe in coincidences," snarled Sharma somewhat hammily. He's certainly got it in for our hero.

Next, it was the turn of the Home Secretary's special advisor and sometime lover Rob Macdonald (Paul Ready), quizzed over his frosty, foul-mouthed relationship with colleague Tahir, their curt phonecall shortly before the blast and why he handed him that crucial case of documents. As Macdonald smiled, snivelled and simpered, virtually leaving a trail of slime across the screen, this one clocked in at a modest four minutes. 

Finally came another seven-minute job, when Budd was drafted in to help extract intel from his old train buddy, coerced would-be bomber Nadia (Anjli Mohindra). Despite DS Rayburn's teeth-gnashingly irritating interruptions, Budd coaxed a lead out of Nadia: her husband had been given the suicide vest by an Asian man in a car park 20 minutes from their home. She lingered tantalisingly over that mugshot of Tahir before shaking her head. 

Added together, these scenes meant that one-third of the episode was taken up with people talking across tables "for the benefit of the tape". We wouldn't have it any other way.

Conspiracies came in every direction

"It wasn't my idea," whined Macdonald to counter-terrorism minister – and now Acting Home Secretary – Mike Travis (Vincent Franklin). The weaselly pair were clearly in cahoots about something, quite possibly luggage-shaped. As Macdonald let slip during his interview: "We were returning his briefcase." "We?" "Er, I."  

Travis, who has a secret hotline to police chief Commander Anne Sampson (Gina McKee), reminded the panicking Macdonald to "stick to his simple, plausible story". Surely this pair of prize plums couldn't have conspired to kill their boss?

There's no shortage of other potential suspects. Sampson herself said Montague "was a dangerous politician who must be stopped". Over at MI5, director general Stephen Hunter-Dunn (Stuart Bowman) and shady accomplice Richard Longcross (Michael Shaeffer) discussed "putting a plan in place". 

The power-hungry Home Secretary had also just blackmailed the Prime Minister (W1A’s David Westhead), who spoke darkly about "forces festering within", and rattled her ex-husband, slippery chief whip Roger Penhaligon (Nicholas Gleaves). "Julia's snatching the keys to Number 10," Penhaligon told Travis. "We need to do something fast."

Meanwhile, the Islamist terrorist cell and the sniper's alleged accomplice remain at large. ISIS even claimed responsibility on Twitter. Yep, Montague had made more enemies than Donald Trump – and some of them hadn't settled for a vengeful New York Times op-ed. 

Spare a thought for Kim – or is she a suspect too?

She only made brief cameos but Budd's straight-talking sidekick PC Kim Knowles (Claire-Louise Cordwell) had become quite the cult character. She alternated between calling him "skip" or "sarge", stoically faced down the egg-chucking protestors and was a dry-witted, pleasingly implacable presence.

It wasn't just Budd, then, who had the wind knocked out of him by news of Kim's fate. Viewers felt the loss too. Kim had been first to spot the danger, sprinted to the stage, took the brunt of the blast and died from her injuries. A heroine until the last. A good egg, you might say. 

However, some eagle-eyed viewers have speculated that Kim might have actually been a double agent and she was the one carrying the explosive, heading for Tahir's side of the stage to make it appear he was the culprit.  Was Budd actually running to the stage to stop her? Is that why he asked "What did Kim say?" during his police interview? 

Lone wolf David is man on a mission

"I want to be part of finding the bastards who did this," said Budd before the credits rolled. He's certainly got the scent of blood in those handsome, flaring nostrils. 

Having swept the venue and checked the briefcase, Budd suspects the bomb was planted backstage at St Matthew's College for Tahir to pick up. He's convinced that professionals "with an agenda" broke into his flat and swapped the bullets in his gun for blanks – but why? 

Somebody, presumably the security services, also wiped 15 minutes of CCTV footage from the Blackwood Hotel which proved that Longcross had visited Montague in her suite. Last seen striding purposefully down the street, it could be time for Budd to go full Jack Bauer-from-24 and solve this mystery solo. Jock Bauer, anyone?

Bodyguarding lingo decoded

Amid all the shock deaths and near-suicides, it was a jargon-lite episode this week. All we got was the usual talk of "PPOs" (personal protection officers) and a "PolSA" sweep of Budd's flat (one overseen by the Police Search Advisor). 

Episode five can't come fast enough

We’re now at the business end of the superlative six-part series and it's becoming increasingly hypnotic. What else does Mercurio have in store? 

A nod too to director John Strickland, a familiar name from Line of Duty, who has taken over from Thomas Vincent for the second half of the series and steered this quieter, more slow-burning episode with real skill. See you back here to dissect the penultimate instalment. Lavender, come in...