I want to take a minute, or two, to talk about Holding Chair. In the future, it may become a Hunger Games-style show in a Black Mirror world where only the toughest survive. If it were on ITV, it would obviously be hosted by one of the usual suspects: Ant and Dec, Joel Dommett, or Alison Hammond. But thankfully, even though we live in scary times, we haven't quite got there yet. At the moment, it's just a way to test cancer patients' resilience in the face of adversity. It starts when a patient receives a message on their phone that an appointment for their next chemotherapy session has been booked.

But instead of a firm date and time, it says "provisional appointment". There is a date but not a time. Ladies and gentlemen, this is the Holding Chair. When I first encountered this scenario, a few weeks after starting treatment for my incurable bowel cancer, I panicked.

I was worried about what would happen if there wasn't a treatment slot for me. Would having it delayed for a day or two be catastrophic for my body's ability to fight my tumours? And I was frustrated because not having a fixed appointment time makes it difficult to plan anything for the day.

I've become a much better contestant at Holding Chair since my first experience more than two years ago. As someone who's going to die alone, I can usually make do with whatever slot I'm given.

But I wonder how parents of young children manage the stress of not knowing until just the night before. How do they sort out taking their children to nursery or school if they suddenly discover they have to be in hospital for 8.30am? And how do grandparents keep their promises to pick up their grandchildren from school in the afternoon if they get told their chemotherapy will start at 2pm?

The official reason for Holding Chair, at least at my "world-leading cancer hospital", is that there are too many patients for the slots they have available so you have to hope another patient is too ill to have treatment and then you can take their slot. (That's the Black Mirror/ Hunger Games/ survival of the fittest bit.)

The unofficial reason, told to me by very reliable sources, is that there is a lot of staff sickness due to both burnout and winter illnesses, so it's rarely possible to predict how many nurses and healthcare assistants will be working. Each nurse can only look after a certain number of patients, so if the staff are sick, the scheduling team has to do a lot of juggling of appointments.

Whatever the reason someone has a Holding Chair slot rather than a definite appointment, it can be a very anxious time. And this is just another reason why I think the NHS needs to get a grip on mental health issues, which is one of the main side effects of cancer.

If they don't, then there'll be a catastrophe of epic proportions in the future.

It won't happen next year or the year after that, but it will happen by the time people who are in their 20s now are in their 50s, 60s, and 70s.

Their anxiety levels are already much higher than they were for my generation when we were their age. Imagine their day-to-day anxiety coupled with the fears that are a natural part of having cancer, along with the Holding Chair anxiety-inducing scenario.

This is why action is needed now. All cancer patients need to have access to mental health support both during and after treatment. And, from a personal perspective, I'd like an appointment system that doesn't involve a Holding Chair.