A saw does not come under knife law, offensive weapon law maybe ( but only if used as one, but then so would a feather duster). The restrictions on knives are on the ability of a knife to stab. Hence why locking knives are classed as fixed blades. Saws do not come under this definition. Bear in mind you could have a fixed blade tenon saw or somesuch. I mean, no ones really going to carry a saw as a weapon, if they have one, they will have a use for it.
Nope it comes under S139 which is Sharply pointed or bladed articals .................a Saw is both
The locking mech and the sub 3" is not relevant that only come in in the exemption which is Specifically for a folding pocket 'knife' which a saw isnt
(This is the only part of S139 that mentions the word 'Knife')
yes it would make formidable weapon and will make a mess of any flesh it cuts making a very difficult wound to deal with
(any body who has had a SAK saw jump and be drawn across a finger knows the mess and hassle a little cut makes)
So yes a copper can if he wants use S139 on a SAW but is less likely to automatically
heres mine
you really wouldnt want this whacked across the face and jugular