James Norton is a rapidly rising star in the acting firmament, playing Grantchester's ruggedly handsome and much-loved vicar Sidney Chambers for three years.
He then smouldered on TV as Andrei Bolkonsky in War & Peace, was the terrifying villain Tommy Lee Royce in BBC1's Happy Valley and banker-turned-gangster Alex Godman in McMafia. He's even been tipped as the next James Bond.
But behind the scenes, what viewers don't see is that James, 33, always has a glass of orange juice to hand on film sets, just in case his blood sugar drops too low. Or that if he's doing a scene without his top on, there'll be a glucose monitor stuck out of sight on his bottom.
Pictured: James Norton in Grantchester. James, 33, has a glucose monitor sticking out of his bottom when filming topless
For James has type 1 diabetes, an autoimmune condition that affects around 300,000 people in the UK and is on the rise.
It occurs when the body's defence system mistakenly attacks beta cells in the pancreas where the hormone insulin is produced (by contrast, type 2 diabetes is linked to poor diet and obesity).
Outwardly, type 1 is an invisible condition: people look healthy. But poorly controlled blood glucose (also known as blood sugar) can wreak havoc, damaging the tissues — particularly the small blood vessels in the eyes, the kidneys and those that supply the nerves in the hands and feet.
James starred in McMafia, where he played the English-raised son of an exiled Russian crime family
He has type 1 diabetes, an autoimmune condition that affects around 300,000 people in the UK and is on the rise. Pictured: In McMafia
Too little blood glucose can lead to 'hypos' (hypoglycaemia), characterised by dizziness and shakiness. If not treated quickly — with a sugary drink or glucose tablet, for example — this can lead to drowsiness and confusion, unconsciousness, or, more rarely, a seizure or coma.
Blood glucose management can be an inexact science; a change in temperature, an adrenaline spurt or catching a cold can send blood glucose rocketing as the body releases a range of substances to deal with stress or fight infection.
'Being in a play is complicated because I might be on stage for up to an hour-and-a-half,' explains James. 'If it's a period drama I'll ask the costume designers to create a hidden pocket where I can stash some sugar tablets.
James has even been tipped as the next James Bond
'Then, if I start to feel shaky, I'll improvise: I'll wander upstage, throw three dextrose tablets in my month and then carry on with the scene. I've lost count of the number of times I've done that.'
But if he now manages his condition well and with good grace, James would be the first to acknowledge the example of his family. And, more recently, the latest diabetes technology — something he believes all people with type 1 diabetes should have access to.
'Within our little nuclear family of four, it's completely normal to have type 1 diabetes; my dad is the only one who doesn't have it,' explains James, who was brought up in North Yorkshire by his parents, Lavinia and Hugh, both teachers, and then studied at Cambridge and RADA.
'My little sister, Jessie, was diagnosed when she was nine. My mum was diagnosed when she was 58 [roughly the same age as Theresa May was when she found out she was type 1].
'Then when I was 22 and just starting out in my acting career, I began to experience the same symptoms. I was losing weight, urinating more often and feeling very tired.'
A blood test confirmed he had type 1 diabetes.
While most people with type 1 are diagnosed between the ages of 16 to 25, it can develop at any age.
Research suggests type 1 is due to a combination of genetic predisposition (there are distant relatives with the condition on both sides of James's family) and some kind of environmental trigger.
He was diagnosed with Type 1 at the age of 22 and is pictured at the fourth annual Talking About Diabetes (TAD) event held at The Royal College of Physicians in London
Despite his family history, the diagnosis still came as a blow.
'It was traumatic, because I'm a terrible hypochondriac anyway,' admits James. 'But it was also manageable because I had the best role model in my sister, who was training to be a doctor. I called her so many times, worrying about things, which was strange, because I'd always been the protective older brother, keeping an eye on Jessie at parties.
'Having type 1 was particularly hard for her through her teenage years when she had so many other things to contend with. But then, when it was my turn, she got me through it, too,' says James, talking to Good Health exclusively at a major conference for families affected by type 1.
'Because my sister had been diagnosed so young, my parents already knew all about management and control, and also the need for that psychological balance between recognising that it's a serious, life-long condition, but not letting it define us,' he says.
I'm painfully aware that not everyone can have the life-changing technology I have
'I know it's terribly hard for parents. But I think being over-protective and restrictive does as much damage as the disease.'
James doesn't follow a special diet and has never cut out sugar. 'If I turn down pudding it's because I need to lose weight for a role, not because of my diabetes,' he says. 'I love chocolate, I love red wine.
'As a family, we're so relaxed about our diabetes. My mum has had to bring needles to film sets because I sometimes forget.
'We don't think of ourselves as a 'diabetic family'. We're just three type 1s getting on with it.'
But there is no doubt that for people with type 1, managing blood sugar levels can be a relentless task, involving frequent (and often painful) finger-pricking throughout the day with a small sharp lance to test blood glucose, and endless calculations about how much insulin to inject to keep levels as close to normal as possible.
There are technologies that reduce this burden. For example, some people rely on an insulin pump, a small electronic device with a tiny cannula (tube) that sits just under the skin. This allows basal insulin (also known as background insulin) to be delivered around the clock. But diabetics still need to give themselves a different, faster-acting insulin, known as a bolus, whenever they eat.
There is also a less invasive way of checking blood glucose, with continuous
