During the treatment, David's immune system took a battering. After those initial courses the father-of-five was admitted into hospital for tougher treatment. "I burst out laughing when they said 'Now for the intensive chemo'. I had gone through all this treatment and now you are going to bring me in for intensive? 

"I was injected twice a day by my wife in the stomach to promote the development of normal cells. 

"Then they took them to Cardiff to have the stem cells harvested and I was put into an isolation unit in Singleton for a stem cell transplant." 

He said: "The final intensive dose of chemo destroys your whole immunity. By reintroducing your own stem cells they hope it will stop the cancer re-establishing itself." David's sporty lifestyle and his fitness stood him in good stead. "The stronger you are, the closer to the brink they can take you." 

Photos at that point reveal him as puffy, pale, with little hair and looking 15 years older than the slim, athletic figure he is now. David was in isolation for four weeks, with his nurse and his wife Rose his only visitors. It was a tense time for all the family, and one from which he made a painstaking recovery.

And he talks about that time now, surrounded by family photos and good wishes cards with emotion in his voice. "I would like to thank people who are totally unaware of what they have done for me - blood donors, for one. "At 3 a.m. one cold February morning the nurse came in and gave me a blood infusion. "I became quite emotional on my own in that room because somebody would  have gone in quietly and given blood, not aware of the impact it was going to have, it was saving my life." 

Once the initial danger had passed David was allowed home, a shadow of his former self. "I remember standing at the bottom of the stairs, looking up and thinking 'I'm never going to be able to get to the top of those stairs'. "But I gradually managed it. Then from here to the gate. Then my wife would take me for a walk along the front. Then I walked my first hole of the golf course. Then three, then nine, then 18 holes and then I played golf for first time. "It was such a sense of victory. And even those terrible scores were fantastic."

 Aside from the time away from his sporting life there are other losses which David feels more keenly.

"I missed my daughter's graduation because I was in hospital." "I see the cancer as the enemy. I'm fighting off the beast. The enemy stopped me doing the job I wanted to do at Maesydderwen."

When David took up the head's role at the Ystradgynlais school he started a plan to rebuild the blocks. It was a labour of love which he wasn't able to enjoy : -

"The cancer stopped me finishing what I had started. I was struck down in July. The new block was due to open in September." But the school held off the official opening until David came out of hospital and, though in very bad shape, he made it to Maesydderwen for an emotional reunion with the children. "One of the hardest things I've ever had to do was to give my final assembly. I had lost all my hair and I wasn't really strong enough. "I didn't want to go to the opening and press the flesh and not have time to talk to the kids, so they arranged a special assembly."

David gave a speech, even though he couldn't stand for long. "The essence of what I said was that I had never come across a child who was bad. I had come across bad behaviour, I had come across children who had been treated badly. "I said 'When you look at yourself in the mirror after being in trouble  just remember, you are not bad.

"Rise through whatever is happening to you and respect yourself.'" David takes a quiet moment to remember the scene. "As I got up to go there was a huge ovation."

 He says leaving the pupils was one of the cruellest blows that his cancer dealt him. He says it is the psychic rewards that keep teachers motivated. Now he gets those rewards solely from his family and the milestones he is determined to mark with them. He and Rose have instilled a work ethic and a love of education into their own children, who are pursuing careers in education, law and children's services. 

And, of course, there are weddings to look forward to. During his recovery David was able to walk one daughter down the aisle and another, Katie, is planning her wedding for next July. "That is something else I am determined to enjoy and, if it hadn't have been for this treatment, I would not have been able to enjoy," he added. "Another son married last September, so I  was able to see his wedding. My youngest daughter has just got a 2:1 in Welsh and we are going to her graduation next week."

 But, understandably, David mourns for his previous life : "I grieve for the health I had, for the person I was. It was emotionally a very traumatic time : "I would get up at 3am, walking the house in turmoil and I would look over my shoulder and Rose would be behind me. "She was the emotional rock I was able to fall back on."

And now as healthy and as energetic as he expects to be, David is using his love of golf to raise money to fight the disease.

 He is calling on Welsh  clubs to donate rounds of golf. "I only started 10  days ago and I've had half a dozen who have donated free rounds of golf and the proceeds can go to Myeloma UK." Some of the funds will also go to the Leukaemia and Lymphoma Fund of Wales, based at Singleton Hospital.

 It has been sport, he believes, that has given him the rules of engagement with his cancer.

"I'm determined it's not going to get the better of me.

"One of the things sport has taught me is how to get a perspective on success and also how to handle defeat.

"The best result I can get from this match is a goalless draw," he laughed.

"But I'm determined to go into extra time."

© South Wales Evening Post