In message , Rob
writes
With access from the inside, and about a 3mm view of the 'bolt' between
the striking plate and the door, what's the best and least destructive
way of removing this (lost key) external door lock?

Thanks, Rob


Angle grinder..........

Seriously an angle grinder with the guard removed and a thin disc, maybe
a shade suicidal but it works well. I removed a window rack bolt this
way only a few weeks ago. If you have 3mm gap you should be able to get
the disc in without damaging the door or frame.

I'm sure some one will come up with less dramatic methods though.

A slightly more sedate method would be to remove the hinge pins if you
can and lift the door out that way,

Failing that a GOOD locksmith should be able to pick it for you in a
couple of minutes.
--
Bill