I have a lot of brothers - five of us are all very close in age. When we were very young (I would have been about six, I think) we used to have motorbike races. Going at furious speed, so consumed with sibling rivalry that we were ready to risk our lives. Of course we weren't going anywhere. We were each perched on an arm of the sofa or one of the chairs of the cheap three-piece suite in the living room. What was great about it was that we were hovering indefinitely in a breathless photo finish, where it seemed that it really might influence the outcome of the race to screw up our faces that bit more, and to make more engine noise - just to get an extra millimetre advantage.
The arm of a chair could be anything - a motorbike, a camel, a horse - I remember setting off on all kinds of perilous adventures - a small but intrepid explorer of imaginative possibilities...
The best game of all was called The Real Live Game.
It felt as if it deserved capital letters. The great days of our Real Live Games were when I was about seven.
We would shut ourselves away in our bedroom and decide on the exact nature of the terrific disaster that had befallen us. Most commonly it was a plane crash in the jungle, with five brothers as the only survivors.
We would act out the crash of course - leaping and screaming, tumbling from the beds, fighting to cut ourselves free of the burning wreck, crawling to safety to discover that we were in a strange new world, lifting our eyes in wonder at the towering trees, the trailing vines, the plunging waterfall, the distant mountains.
Birds sang, howler monkeys howled, snakes hissed, panthers growled.
There were perils on every side - staring eyes watched from the undergrowth as we salvaged what we could of the wreckage, fashioned simple weapons, and set off through the trees.
I remember the game as a kind of timeless ecstasy - it wasn't anything so dull as fun, it was life and death.
My older brother was always the most resourceful of us - he took the lead as we foraged for food and hunted prey, as we built a simple shelter, and struggled to light a fire, there in the middle of the bedroom carpet.
And there was a clear objective truth, beyond the game, that we absolutely understood, that we were indeed a strange tribe of misfits struggling to make our way in a new, threatening world.
The game was a solemn preparation for life - like a magic spell or ritual. We knew that if it worked in that secret space amongst ourselves it could work in the big world out there as well.
And it has, more or less.
My job, as a grown up, is playing - a deadly serious business.
My new book 'Lost in the Toy Museum' is published by Walker Books.