Most likely the clutch plate stuck to the flywheel, often happens. You can try starting it in gear and when it goes stamp on the break pedal, quite fun kangarooing down the street, but be ready to switch off if it doesn't release.
From the mechanical section on the home page
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Stuck Clutch
First of all make sure the hydaulics are working. You'll need somebody looking underneath whilst you push the pedal. If the pushrod from the slave cylinder is moving the clutch operating lever back and forth then it's not that. Stuck clutches are far more fun. Warm up the engine. Stop it. Put it in first and restart the engine so that your Commer starts to move. With your left foot, depress clutch pedal (it's vital the hydraulics are working, as above) and then with right foot stamp on the other two pedals alternately, going on and off the throttle and brakes. The shunting will either free it all up with a bang, or you run out of road. It's normally just a bit of corrosion on the flywheel sticking stuff together. This method does work, my Commer sits in a field all winter and it happens every year. [Andy Zarse]'
A more gentle method is to warm the engine up thoroughly and jam the pedal down over night, usually does the trick but sometimes needs a couple of goes.