DID tonight’s thrill-a-minute episode pass in too much of a blur? Here are ten of the finer plot points you may have missed - and some lingering mysteries. Warning: contains spoilers.

Q: Who was the boyfriend of Budd’s ex-wife, Vicky?

A: Meet Mr R Herring, straight from the shoal of dead ends. Writer Jed Mercurio had teased viewers about the boyfriend’s identity, never allowing him to be seen or heard. Perhaps he did not exist, and was being used by Vicky as a way of trying to convince her estranged husband that there was no chance of a reconciliation.

Q: Why didn’t Budd tell his police colleagues he knew the sniper, Andy Apsted, from his Army days?

A: He thought the threat had passed when Apsted killed himself. When Julia fell victim to another assassination attempt it was too late to reveal the connection without making himself look complicit. By that point, the only way for Budd to prove his innocence was to find the guilty party.

Q: Why was Budd trying to buy a rifle on the black market?

A: It was not just any old rifle he was after. He was after the same specialist type that he knew Apsted had used. Whoever had the connections to supply this had put Apsted up to the crime.

Q: Why did it take till the last episode to link Apsted with Budd?

A: Unknown. All Apsted’s associates were supposed to be identified and cross checked. One might have thought Budd would have shown up early on, unless police were searching backwards from Z to A.

Q: Why did Budd keep counter terrorism officer Louise Rayburn in the dark?

A: Rayburn had been a good friend to Budd, tipping him off on several crucial developments. He kept quiet because he did not know how far the conspiracy went, and could not risk what he had found out becoming common knowledge.

Q: Why did Budd make sure the security services got to his flat before the police?

A: To prove they knew about the kompromat (compromising material) that Montague had been given.

Q: Why did Budd insist on defusing the bomb himself?

A: He was not sure how much longer he could maintain pressure on the dead man’s switch, so any expert who tried to help was in danger of being blown up with Budd. He knew this was the same type of device worn by the would-be suicide train bomber in episode one. Since the other vests had been blown up, that meant he was wearing crucial evidence that could lead forensics to the bombmaker and prevent further attacks. Moreover, putting himself in danger showed police he could be trusted.

Q: How did Budd know where Chanel the dodgy PR lived?

A: Perhaps from her personnel file when she was working for Home Secretary Julia Montague? Also intriguing is how he gained entry to her flat.

Q: Why did someone switch live rounds for blanks so that Budd’s suicide bid failed? Why not simply take his gun?

A: If they had taken the firearm from Budd’s hiding place he would have known straight away that someone had been in his flat. Inserting blanks made sure their fall guy was safe. “They were trying to frame me,” explained Budd. “I suppose they couldn’t take the chance of leaving me with live rounds.”

Q: Is Mercurio now a shoo-in for a Bafta?

A: Although previous works, Bodies and Cardiac Arrest, were nominated for Baftas, Mercurio has not won one. He has scooped other prizes, including a Royal Television Society award for Line of Duty.