A likeable everyman, Jamie is the underdog we should be rooting for. His flaws are a lack of assertiveness, an overfondness for routine and a tendency to get stressed.
The branch manager of a suburban bank in Slough, he lacks the drive to force his way up the corporate ladder. It is incredibly tedious work but he finds the deadening routine comforting: he has had enough surprises for a lifetime following the disappearance of his beloved wife Layla seven years ago, which haunts and defines him still.
Jamie shares a house with his best mate, Dave, who he's known since school, though they're polar opposites. Jamie's very close to his mum Paula, but he never knew his dad and she always claimed he was the product of an ill-advised one-night stand. However, his background isn't all that it seems...
As well as being a devoted mum to Jamie, Paula is a nurse.
She's caring and tough, doesn't suffer fools and hates moaners. She's always put Jamie first and now he's an adult she can be a bit overbearing, though her meddling is well-intentioned.
Paula doesn't think Dave is a good influence on her son and has always encouraged Jamie to find new friends. The one thing she and Dave do agree on, though, is that Jamie needs to move on from Layla.
Dave is Jamie's hedonistic best friend, who encourages him to grab what's left of life by the balls.
Laid-back, with a what-will-be-will-be attitude to most things in life, his main vocation is annoying Jamie, a task he approaches with a focus and energy lacking in all other aspects of his life.
Dave genuinely cares about his best mate. He knows that Jamie is still hurting badly over Layla, but also realises that he needs to get out of his self-imposed rut.
Dave has never really got going or achieved much, so his response to the apocalypse is to create a bucket list of things he's always wanted to do.
An unlikely hero, Rhonda is a mild-mannered librarian who has never broken a law in her life. So she is utterly unsuited to living in a maximum security prison, which is where we first meet her.
She has been sent down for a crime she didn't commit, and is absolutely terrified. Rhonda is intensely devoted to her family and it is this love and the determination to be reunited with them that will get her through the extraordinary set of events she is about to endure.
Leanne is deeply flawed, morally ambiguous and utterly shameless.
Her world-view is totally reprehensible yet, somehow, she retains a certain charm. She is brave and loyal to her friends, and while she's the kind of person Rhonda would normally avoid, she's exactly the sidekick she needs during these extraordinary times.
Being strong-willed, street-smart and adept at stealing, Leanne is uniquely suited to apocalyptic life.
Charismatic, rebellious and incredibly politically incorrect, Father Jude isn't your typical priest. He drinks too much, smokes like a chimney and swears like a docker.
But don't be fooled by the exterior: underneath he is a deeply moral man with a profound and passionate Christian faith. He just doesn't believe you need to be devoid of fun to be devout.
He understands that human beings are fundamentally flawed and though he is a pious man, he knows that the church is not God, and that to criticise it is not blasphemy. In fact, he sees uncovering wrongdoing and corruption as a demonstration of his love for God: an attempt to make the church more sacred.
Jude hates hypocrisy and bureaucracy, and he enjoys annoying anyone he perceives as pompous, prudish or pious. When Sister Celine arrives at the Vatican, he sees her as a breath of fresh air.
A wide-eyed and innocent nun, Sister Celine is thrust into the heart of the Vatican having previously led a very sheltered life.
Optimistic, humble and non-judgmental, Celine is a self-taught linguist and now speaks six languages, a talent that enables her to get an interview for the position of research assistant to Father Jude.
When news of the apocalypse breaks, Celine is thrust into an extraordinary quest that not only takes her way out of her comfort zone, but also causes her to question everything she knows.
A career soldier with a natural sense of authority and a flair for leadership, Gaines is courageous, tenacious, and believes in putting his duty above his feelings. As a result, he has risen through the ranks of the army, although for the last few years he has stepped back from active duty to drive a desk in Washington and the Special Situations Group comes under his remit.
Gaines is incredibly loyal and despises hypocrisy. A true stoic, he feels uncomfortable with excessive displays of emotion. He doesn't care about anyone else's private life, so his is none of anybody else's business either.
Scotty is a minor Washington bureaucrat. His background is astrophysics but after gaining his doctorate he left academia to join the Special Situations Group, a largely forgotten (and woefully underfunded) department responsible for planning the official US government response to apocalyptic scenarios.
Having spent years toiling in obscurity, devising plans he never thought would see the light of day, Scotty finds himself unexpectedly thrust into the centre of events as a result of the comet. Despite his extreme intelligence, he is sorely lacking confidence and occasionally paralysed by self-doubt.