When you look at how the Park setting works in an automatic transmission, you can see how this could happen. Basically, Park is engaged by a small pin that (typically) slides into the transmission’s output shaft and locks it, preventing the shaft from turning and effectively locking the drive wheels.

The problem is that the Park pin (also called a pawl) is almost comically small for the job it has to do. The point being that Park pawls have been known to fail, at which point, the car will be free to move if the park brake isn’t applied.

Best practice when parking an automatic car is to stop where you want to park, but leave the transmission in Drive and apply the foot brake. Then apply the park-brake, take your foot off the brake and let the park brake take the weight of the car. Then select Park. You’ll still have the security of being in Park, but you won’t have the car’s weight resting on that little park pawl.

For a start, it’s never a good idea to drag a car anywhere with the wheels, hand-brake and steering locked. You can damage anything from the transmission, steering column, driveline and even ruin (flat-spot) the tyres.

If the clicking noise when you drive it wasn’t there before, then a mechanic would suspect that there’s been damage done to the front driveshafts. This would be consistent with the car being forcibly dragged along the ground. If you’re worried, have a mechanic check the car over and send the repair bill to your (now possibly ex-) housemate.

There are two possibilities here and it will all depend on whether your car is a 2005 model (that was first sold in 2006) or a post-facelift model and also whether it’s a TS Astra or an AH model Astra. If it’s the earlier car, then you might be in luck. The process involves taking the new key, placing it in the ignition and turning the ignition on (without starting the engine). Then, when all the dashboard lights are lit up, you press one of the remote buttons on the key. And that’s about it. You should hear the car lock and then unlock itself to let you know the process is complete and you’re good to go.

For post-2005 models, however, things are not so simple. In this case, you need to either visit a locksmith or a workshop that has the Holden diagnostic gear, as the new key needs to be coded to the car via the diagnostic port. That said, I’d give the first method a try before spending money at a workshop. Who knows, you might just get lucky.