I nearly choked on my muesli when I opened a letter from my old school inviting me to give the annual prize-giving speech.
Am I really that old, I thought? Besides, my time there was not happy, so I have never been back: but I accepted the chance to enthuse a new generation of boys about charity work.
When I arrived, I was astonished to find many of my old teachers were still there - looking a little more wrinkled and being unnervingly nice to me, but otherwise untouched by time. Somehow I got through the small talk beforehand without calling any of them "sir". Even so, as I stood up it felt like they were marking my speech.
I began by cracking a few jokes about old fossils, and got a few more laughs by exploring the psychological similarities between head teachers and psychopaths. Then I got to the heart of the matter: whether the boys should consider careers in the charity sector. Initially I advised them to "take the money - become a lawyer. No one will like you, but at least you'll be rich."
It's a fair point, one that I ponder each time I read my bank statements. But then I went on to recall the African famines that I had played a small part in relieving and the happy faces of the very ill children we care for at Julia's House. Finally, I looked at the healthy faces of the boys in front of me and I wished them a long life, at the end of which they could say: "I made a difference with my life. I left the world a better place than I found it."
I didn't say that, as a charity worker, your innovative social impact will usually be ignored rather than modelled by successive governments.
I didn't mention wading through commissioning contracts, or waging tiresome campaigns to stop back-of-the-envelope policies from creating unintended hindrances for charities. Who wants to disillusion the young?
I didn't say that the media usually gives you a platform only if you are beautiful, in the depths of personal tragedy or likely to embarrass a minister in public - or preferably all three. Or that we shouldn't have to beg for money for things that are cost-effective and just. Or that if trustees lack integrity, your idealism will be crushed in a head-on collision with reality. Far better to give them hope. So I gave it my all, stoking the fires of their dreams.
I drove away from the grand old buildings where I had once learned so much and yet enjoyed myself so little, ancient ghosts receding behind me and finally put to rest. A charity worker was an unusual choice of speaker, for people like me are not deemed to have 'made it' in life. But I can still hear the hush in the audience when I told them that riches do not matter, nor does the car you drive, nor the clothes you wear; it is the things that you do for your fellow human beings that you will be remembered for.
And for the ones who might follow me into this sector, I shall keep my fingers crossed.
Martin Edwards is chief executive of the children's hospice Julia's House