Now he lives on an Pounds 11,000-a-year retirement pension and spends his time as a LibDem councillor and chai .rman of the Friends of Highcliffe Castle, in Dorset, an 1830s stately home of the "romantic picturesque style" which he and his wife Barbara are helping to restore.
He said: "I used to work an 80-hour week as a head and 30 or 40 hours on top of that for everything else. I lived on five hours' sleep per night for 20 years. Now I have time to reappraise, to be a bit more sensible and do things with a bit more grace."
Mr Nicholson, the former head of West Moors middle school in Bournemouth, had never contemplated retiring at 50. But when he decided to make the sacrifice he had to face some stark financial truths. Although he was given a Pounds 40,000 lump sum, he was denied any enhancement and had to forgo a redundancy pay-off. If he had been a deputy head retiring because of budget cuts, he would have received six years' enhancement from Dorset education authority which would have boosted his lump sum and his pension. "All in all," he said, "I gave up at least Pounds 330,000 in salary over the next 10 years and missed out Pounds 60,000 in redundancy and enhancement payments."
In the short-term his disposable income has not changed greatly. He used the lump sum to pay off part of his mortgage which had been costing Pounds 800 per month and considering the high pension contributions he was making when working, the Pounds 11,000-a-year pension has worked out as a 50 per cent rather than two-thirds reduction in salary.
He said: "Value in life should not be equated with being paid for it. Once I took the plunge I relaxed. Society thrives on fear about the future but if you can't afford to buy a new car you buy a secondhand one or you walk. I now cycle and walk as much as I can. Although I enjoyed my career, I did not enjoy the nonsense of the last 15 years."
Since his decision, Mr Nicholson has been contacted by many teachers and several heads contemplating early retirement. He said:"Teachers have rung me up and asked what it's like and I tell them that you have to be upbeat."
However, he felt many were not aware of all the financial ramifications. He said: "Teachers are very trusting and they expect that the system will give them a proper deal. The profession should seek to be better informed about pension entitlement."