My early victorian building has a nice stone facade covering what
looks like a messy mix of mortar and rubble.

I want to fit a combi boiler and need to drill a 10cm hole for the flu
pipe. How can I neatly cut such a hole through this type of wall ?

My neighbours did this recently but it seemed that the builder took
three days and from the appearance and size of the resultant hole he
must have done it with a pick axe! I would like to be somewhat
tidier.