If your classic car has been laid up for a long time, there is a chance that the clutch may have ‘stuck’. The friction disc is held tightly between the flywheel and the pressure plate when the pedal’s released. When the car stands unused for a long time, the disc may start to adhere to the flywheel and pressure plate. This may be due to rust or to the resins used to manufacture the friction material. To free it, you can probably shock it free. Warm the engine up in neutral, stop it, engage first gear then restart it with the clutch depressed. It’s helpful to have a space in front of the car, because if this doesn’t free it then the shocks produced by kangarooing out of the parking space often will. Alternatively, secure it firmly on axle stands with the driven wheel elevated, start it in third gear, run it up to 20 or 30mph, then slam the brakes on. It’s wise to chock the undriven wheels before attempting this – and make sure there’s some space in front of the car in case of a mishap.
Hmm the first method is the best, has worked for me many times on customers cars, if you have disc brakes and use method two you risk shearing the small brake disc retaining screws as the brakes are hyper-effective when they don't have the weight and momentum of a moving car to deal with, I did it once I ended up having to use an easy out to remove the remains of the retaining screws.
Mmm! Sometimes starting a car in 1st gear can bend the shaft of the starter motor where it’s an inertia type. Warm the engine up thoroughly, sometimes this is enough if you let it heat soak. Then in a clear space, helps if it’s on a slope and with help. Engage gear, 2nd or 3rd, turn on the ignition and push the car forward. When it starts, down clutch and brake hard. Or roll the car with engine running forward and snick it into 2nd gear. Again when driving forward, drop the clutch and brake. Works every time for me. Interesting that inline engines “stick” more transverse.
I have, in the distant, past had this problem (stuck clutch) but I recommend using top gear not first. This puts less stress on the transmission and there is less 'elasticity' between the engine and rear wheels giving greater impetus to the clutch. There is less likelihood of the car leaping forward (if you have the brakes on) because the torque at the driven wheels is less than a quarter of that if first gear is used. If the car is off the ground, have the driven wheels attached, start the engine (still in top gear and with the brake released) and blip the throttle to cause the clutch to experience + and -be torque. Do watch the engine speed ( or the speedo) to avoid dangerous vibrations and bear in mind that if the brakes are binding on one driven wheel the other will be running at twice the speed.