Yeah- you have to pull the trigger. The intercepting sear is essentially a second sear that is released only when the trigger is pulled.
If the sear happens to release (say if you fall and the gun is jarred) the interceptor will prevent the tumble from moving but you needn't recock. If you then pull the trigger it will release the safety sear and the gun will discharge.
OWD- those pix you found are enlightening. The external hammer gun does not have an interceptor sear.
The close-up of the bar-action shows the interceptor very well. The double stub pointing out at you near the right of the lock has two parts: one for the sear and the other for the interceptor and both need to be lifted by the trigger action to fire the gun.
Gnomon,I have to disagree with your second paragraph.
On most British guns, operating a Deeley, Scott or later H&H type interceptor sear, the tumbler does move if the sear is lifted out of bent. It is then caught after a few degrees of movement by the interceptor sear. The whole mechanism must be fully re-cocked to reset the main sear in the bent. IF the lock is operating correctly, you should NOT be able to fire the lock by squeezing the trigger while held by the interceptor sear as it operates like a 'half-cock' bent on a non-rebounding lock and locks the tumbler in a safe position until re-cocked.
As regards the usefulness of an interceptor sear (as posted before), they not only help if a sear is jarred out of bent but also hold a un-fully cocked tumbler back from the striker if the gun is loaded but not opened enough to get the sear into the bent. To do this the intercepting sear must operate part way through the tumbler's swing, not in synchronicity with the main sear.
My Blanch back action suffered from this problem exactly as it ejected rather too early. It took me more than a minute or two to work out what was happening but I am eternally grateful (so is my dog!) that it works like that!
