Q

In Dr. No, the character isn't called Q yet. He's Major Boothroyd, the service armourer, played by Peter Burton in a single scene. On M's orders, he takes away Bond's Beretta and hands him the Walther PPK, which becomes the agent's gun for decades.

Desmond Llewelyn takes over in From Russia with Love, still as Boothroyd, and hands Bond a briefcase full of surprises: a hidden knife, gold sovereigns, a folding rifle and a gas cartridge for anyone who opens it the wrong way. The case saves Bond on the train.

In Goldfinger he's called Q for the first time and introduces the Aston Martin DB5, with machine guns, revolving plates and an ejector seat. When Bond thinks the seat is a joke, Q replies that he never jokes about his work. That sets up the routine that runs for decades: Q explains the gadget with little patience, and Bond fiddles with everything.

With Roger Moore, Q gets out of the lab more and more. In The Spy Who Loved Me he sets up a workshop in Egypt and delivers the Lotus Esprit that turns into a submarine. In Moonraker he watches on TV as Bond comes back from space. In Octopussy he travels to India, helps in the final assault and even flies a hot-air balloon with a Union Jack on it.

In Licence to Kill, Bond loses his licence and goes rogue. Q turns up at his hotel in Isthmus claiming to be on leave, carrying a case of tricks: explosive toothpaste, a camera that becomes a rifle keyed to Bond's palm print, and a detonator disguised as a cigarette pack. He reminds Bond that if it weren't for Q Branch, he'd have been dead long ago. It's Llewelyn's biggest role in the series.

In The World Is Not Enough, Q introduces the assistant who will replace him, played by John Cleese, and Bond nicknames him R. Before leaving, Q gives Bond two lessons from a lifetime: never let them see you bleed, and always have an escape plan. Then he's lowered out of sight through the floor. Desmond Llewelyn died in a car crash shortly after the premiere.

In Die Another Day, Cleese is the new Q and delivers the Aston Martin Vanquish, which can turn invisible. Bond ends up admitting the new man knows his stuff.

In the Craig era, Q is a young computer genius played by Ben Whishaw. In Skyfall he meets Bond at the National Gallery and hands him just a gun and a radio, asking if he was expecting an exploding pen. Later, by plugging Raoul Silva's laptop into the MI6 network, he opens the doors for the villain's escape.

In Spectre, Q helps Bond behind M's back, travels to Austria and uncovers the link between the villains Bond has faced. In the end, he hacks the surveillance network SPECTRE wanted to control. In No Time to Die, Bond and Moneypenny show up at his home just as he's expecting a date, and Q tracks Bond's enemy to the final island.

In Ian Fleming's novels, Q Branch is only mentioned, and the character who appears is Major Boothroyd, the service armourer, introduced in Dr. No. The name comes from Geoffrey Boothroyd, a Glasgow firearms expert who wrote to Fleming criticizing Bond's gun and suggesting the Walther PPK. Desmond Llewelyn played the part in 17 films, more than any other actor in the series.