I had this problem a couple of months ago in my VT and also in my old VR. Will try to explain the best i can...
This will get your car home but you will need to have the barrel repaired.
The barrel has a rod that is attached at one end to where the key is inserted and the other end of the rod will be a round black plastic holder that the rod is inserted in with wires running from it to start the car etc when the key is turned.
What happens is the rod breaks and either gets stuck or turns freely both resulting in the engine not going coz the key wont turn or turns freely. What you have to do is access the left hand side of this assembly eg the other end that the rod is going into. So the plastic surrounds from around the steering column have to be removed.Once they have been removed you should be able to see how to unscrew and remove the round black holder on the left side of the column.Leave all wires intact dont disconnect any wires only the plastic round assembly.You should find a broken rod still inserted in this holderor a piece of rod,just remove that.
Next you will have seen on a vt that there are two metal tabs around the ignition where the key is inserted, for the car to start the key must make contact with this eg leave the key in the ignition.Now use a flat blade screwdriver that will fit into the hole that the rod came out of and turn.You should now be able to start the car.Hope this helps.Wish i could be more detailed but its been a couple of months since pulling the assembly apart so im going off memory.....