So, you’ve given blood once or twice before and thought that platelet donation would be much the same? You fool.

The first difference is when the nurse breezily announces that the process takes on average 90 minutes. You gulp, and think of all the great books you could have bought to fill in the time. She assures you that they have plenty of newspapers and magazines. The Daily Mirror, Men’s Health … tears begin to come to your eyes.

Oh, and DVDs. You begin to perk up.

The second difference is when you are introduced to the Machine, a cross between a school chemistry experiment and a bad Dr Who special effect from the time when everyone knew you could tell a really advanced computer by the number of moving parts. And this is the really clever bit. It sucks your blood out, and you get to see it go down the tubes and squirt itself around a small plastic labyrinth (that’s the school chemistry bit). It then pumps into something like an unfeasibly long transparent condom which gets spun around in the machine’s innards. The platelets separate out and manifest in a clear plastic bag as a cloudy yellow liquid a bit like cheap consommé, or that stuff that floats to the top when you leave gravy in the fridge too long. And then the machine pumps the rest of it, which is still red, back into you. Therefore you don’t actually lose much, and can just get up and walk away when they unplug you 90 minutes later.

You feel tingling in your lips, making you feel strangely like you’re holding back tears even though you aren’t, which is an effect of the anti-coagulant they pump into you along with your returning blood. Otherwise the only real discomfort is sitting in the seat, something a bit like a dentist’s chair, for so long.

The guy who was scheduled alongside me had to pop out to phone a flatmate and alert him to a delivery from Tesco, so I was plugged in first and I got the unit’s sole DVD player. I got to watch Sliding Doors, an enjoyable bit of fluff with Mrs Martin which I hadn’t seen before. It’s a 95 minute movie for what turned out to be an 85 minute session, but they kindly let me finish it.

So, I get to do some good, lose a little consommé and suffer driving to the JR in rush hour, which frankly is the worst bit. Oh, and I get dinner three hours later than normal, but the sting of that is offset by an understanding wife who sticks an extra banana and kitkat in with my lunch. In return unknown strangers that I will never meet in this life with leukaemia or other disorderly nasties will benefit and, who knows, maybe lives will be saved. The good outweighs the bad.

Will probably do it again, and next time I’ll take a book.