The three part series follows Mark Cobden (played by Bean), a remorseful teacher sentenced to four years in prison after accidentally killing someone.
As he struggles to adapt to his new surroundings, he confides in a prison officer (played by Graham), who says he will help him.
But while fans are raving about how good Jimmy McGovern's latest series is, some have noticed something strange about Sean Bean's character and his mum June, played by The Royle Family star Sue Johnston.
While Sue is a great actor, viewers found it strange that she was cast, as 77-year-old Sue is only 15 years older than 62-year-old Sean, and took to Twitter to question the decision.
"Sue Johnston must have been mid teens when she gave birth to Sean Bean," one viewer wrote.
"Sue Johnston is 15 years older than Sean Bean," a second said. "Interesting casting."
"Sue Johnston, born 1943. Sean Bean, born 1959. She was a young mother," a third said.
"Sue Johnston is 77. Why is she playing the mother of a 62 year old Sean Bean?" a fourth queried, while a fifth said: "I assumed Sue Johnston would be his wife not his mum. She's 77, only 15 years older than Sean Bean."
Sue and Sean have previously acted together. Thirty years ago, she played Sean's devoted lover in detective drama Inspector Morse.
The actor has since hit out at sexism in acting. She told The Daily Mail: "That's what happens to actresses in the theatre or TV business.
"Men stay the same and women get to be mothers.
"I play Sean Bean's mother. Now, the last time I worked with Sean in Inspector Morse, I was his lover and now I'm his mother. And that's what happens to actresses."
Time airs on BBC One on Sundays at 9pm, or is available to watch in its entirety on BBC iPlayer.
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