Welcome here - although not under such circumstances. !
This problem didn't show after you'd been parked down the pub - and your 'mates' swapped over the plugleads ?
Seriously though, you sound as though you suspect the timing has slipped. Did it need readjusting ?
1st thing to do with all such cases is to try a NEW set of spark plugs.
Amazing what this will fix - if they are fouled or sooted, no amount of anything will make them return to life.
Failing that, checking everything else is probably on the menu.
Got fuel, its getting to the carb, and can be tickled.
Got compression, when you kick it over.
Strong spark on the plugs, when you remove them and lay them on the head, lead still attached.
If still no joy, remove an exhaust rocker cover, and verify the exhaust rocker(s) still go up and down.
And check rocker clearances.
I'd put money on those spark plugs.
But still check the plugs leads are on the right plugs.
Magnetoes can go duff with little or no warning, points can be dirty or oiled, etc.
Good luck, tell us how it goes, or ask away - and what fixed it.
BTW, the timing should always be set by ALWAYS rotating the engine forward, in the norrmal direction of rotation.
Turning it backwards at any point can allow all the backlashes to accumulate, and the timing can thus be way out...