FEAR not, dear reader. For the first time in many a day you are encountering a column which is not about the coalition; instead, it is more to do with coagulation.

The story starts in 2007, when I was heading abroad on a job and a condition of going was I needed to know my blood group. One way of finding out was to become a blood donor, so I thought great, I could sort a problem and do something I’d been meaning to for years.

It couldn’t have been easier, as the National Blood Service was holding a session at the National Centre For Early Music, within a few yards of my workplace. Soon I had contributed my first pint. I can’t remember if I had tea and biscuits but I’m sure they were offered; an all-round positive experience.

Since then, I have managed to exactly double my contribution to the national blood stocks. Yes, that’s one more pint in nearly three years.

How has this happened? Well, there have been the usual things like not being able to make donor sessions, or the sessions being completely full (we do seem quite good at doing our bit in York).

But on more occasions than I care to remember I have been turned away, with expressions of regret and even offers of tea and biscuits, plus a donor’s key ring, which I use, albeit rather guiltily.

My first non-donation followed my return from abroad, complete with a leg injury which required surgery. Some time after that I still wasn’t very mobile, but it didn’t seem too far to get to the NCEM. Silly me; the staff took one look at me coming in on crutches and politely suggested I come back after I’d been cleared by a doctor. I mentioned this later to the consultant dealing with my leg, who said he didn’t know any reason why I couldn’t have given blood.

The next rejection was because I’d been in a malarial zone during the trip when I injured my leg. I protested I had been back the necessary time; I was told the time limit for donating after being in such a zone had changed.

In 2008, I had my gall bladder removed. While I was recovering, I got a letter inviting me to a donor session, and phoned to say I didn’t feel up to it; the woman I spoke to seemed mildly disappointed. The irony was added to when I did go the next session, only to be sent away – but not because of the operation. No, it was because before the op I had an endoscopy, where they put a camera into your stomach, and this procedure apparently carries a risk of infection.

Some time after that, I managed to donate my second pint, which made me feel a bit better about the key ring and the biscuits, and the fact I seemed to have become a sort of Tony Hancock in reverse. That was until last week, when I rang up to make an appointment, to find questions raised about some medication I’m on (for my stomach, in case you’re wondering) which hadn’t caused any concerns when I gave that last lot of blood. The matter was cleared up, but by then the session was fully booked.

Now, I’m afraid this catalogue of failure cannot simply be explained by the zealous protection of our national blood stocks and a string of unfortunate coincidences – there is clearly some terrible reason why the authorities don’t want my blood anywhere near the NHS, and they’re finding almost any excuse to avoid telling me what it is.

So determined am I to get to the truth that I’ve already made my next donor appointment, and I encourage you to do the same, because your blood really will save lives – even if mine won’t for a little while yet.

•To enrol as a blood donor, phone 0300 1232323 or go to blood.co.uk