A COURT of law and a theatrical performance are similar in numerous ways. Law courts have provided themes for many memorable plays and movies. Today, we are taking in Richard Eyre’s filming of Ian McEwan’s screenplay adaptation of his own novel.

I’m currently enjoying repeat broadcasts of Martin Shaw playing Judge John Deed, slayer of metaphorical jurisprudential dragons for 29 episodes harking back to the turn of the century. “The Children Act” is a close cousin to that theme. And for High Court Judge Fiona Maye confronting the sort of decision-making crisis that John Deed must negotiate, it stars Emma Thompson. For me, that’s bliss.

The issue about which McEwan wrote arises under the UK’s Children Act, enacted in 1989, amended 2004. It begins with a clear statement of intent, that children’s welfare should be the paramount concern of the courts.

At age 17 years and nine months, Adam (Fionn Whitehead) has leukaemia. Two medications are available for treating it. But they first require the patient to receive a blood transfusion. Adam’s parents must agree to that going ahead.

But the family are Jehovah’s Witnesses, for whom blood transfusions are forbidden for reasons that the film’s opening passages explain. For the next three months Adam will remain a child as the Act defines. And in any case, he’s an intelligent young man who agrees that it’s contrary to his belief.

In coming to her decision, Judge Maye takes the unconventional step of visiting Adam in hospital to ask how he wishes to proceed and why it should be so. The film’s second half deals with the sequel to her judgement. The film’s dramatic environment is made more difficult (for Fiona, not the filmgoer) by the fact that her husband (Stanley Tucci) has dropped a bombshell into domesticity. He plans to have an affair. And Adam, after recovery, begins to follow her, rather short of stalking but certainly unwelcome and discombobulating.

The phrase best summarising Fiona is dominant to a plot full of new challenges for which her professional and private lives have not prepared her. Emma Thompson’s portrayal of her is all you might expect. One word covers it. Superb. Or any other synonym.

At Capitol 6 and Palace Electric