"He runs the Embassy in Washington, and the only place you can go from there is Ambassador," says Neil of his character Phil Lonsdale.
"But he won't make Ambassador because he's too good at what he does.
"He's the safe pair of hands - the Ambassador's minder who makes sure that everyone stays on message. He carries a huge responsibility, which is why he will never get the very top job. That's ironic, but true.
"I knew the research had already been done - all you, as actors, have to do then is populate that research with believable characters.
"It's important that you get the little things right, otherwise no one will believe you on the big things.
"That's why in the Embassy you have to use the right terminology and etiquette. This drama is not just poignant and incisive and witty; it also exists in an utterly credible universe.
"We're at a heightened state of alert - and the drama reflects that. It's especially hot on the constant tensions between so-called allies. There's a lot of jockeying for position between agencies on both sides of the Atlantic.
"They all want credit when things go right and instantly pass the buck when they go wrong. No one is suggesting we've made a documentary here, but top-quality drama can add to the debate or ensure it continues. That can only be healthy."
Neil's best known for his roles in cop drama Between the Lines and satirical comedy Drop the Dead Donkey.
