A silence descends over the dusty arena that is the school playing field. Confrontation is in the air. Nerves twitch and muscles tense. The world grinds steadily to a halt. There is no going back now. Control your breathing. Try to relax. Maintain focus. Get ready and .

An explosion shocks the world into action. The chase is on. The baying and whooping of the crowd is barely audible amid the pounding of feet and the gasping for breath. And though I try with several fibres of my being to keep up with the pack, it is no use. I am hopelessly lost - or rather last. Ignominy, humiliation and ridicule will be my fate.

To be honest, I’m not the athlete I imagine I once was, and the blue riband highlight of our school’s sports day - the staff 100m dash - can no longer be classed as my best event. In the time it takes me to travel 20 metres up the track the race is already over. The sight of a young, irritatingly athletic and in every sense dashing Mr Twist, grinning handsomely at his adoring fans and pausing to make Usain Bolt poses for the cameras, takes the wind out of my lungs and leaves me gasping at the sheer unfairness of the ageing process.

Of course, that’s the problem, isn’t it? I’m not getting any younger. The years are not only catching up with me - they’re overtaking me, giving me the rods and telling me to get off the road grandad. And while I might, like King Canute - or Cnut, as those with a taste for mischievous anagrams prefer to spell him - try to turn back the tide of years, the reality is it’s never going to happen.

There is a moment - technically I think it’s called hitting the wall - when my heart and legs tell me I can go no further. That I should give in now, step off the track and disappear up my own dust trail. But apparently there is no longer provision for this in the rules. The head assures me that continuing to the bitter end is in my contract and cannot be renegotiated.

So with those grainy 1954 images of Jim Peters collapsing out of the Empire Games Marathon in Vancouver in the forefront of my mind, I slow my pace, shorten my stride pattern and trundle towards what appears to be an ever receding finish line. There I will accept with equanimity the cruel comments and derisory laughter that accompany failure. There I will acknowledge with smiling good humour the half-hearted clapping and the hollow cheers for having taken part in the first place. There I will, in a spirit of self-mockery, punch the air and strike a celebratory pose.

But of course, all that will be on the outside. On the inside I will curse the blight of age-related joint pain, the fibrous adhesions around my knees and the tendinitis in my right ankle. I will curse the frozenness of my left shoulder, the irritability of my bowel and the pain in the arse- ness of my haemorrhoids. I will curse the highness of my blood pressure, the lowness of my testosterone and the spread of my middle-age gut. I will curse the physical and mental toll that too many years trying to keep pace with ever livelier classes of primary-aged children has wrought.

But most of all, I will curse David Cameron and his proposal to move the age at which teachers can retire so far down the track I’ll need a mobility scooter to carry me over it.

Steve Eddison is a key stage 2 teacher in Sheffield.

Mike Kent is on holiday.