This isn't a knife, it's a saw. So the knife laws don't apply. Anyone can carry a saw (Woodmen, carpenters, etc.). So yes, there should be no problem with carrying a saw in open land.
UK law states the legal carry for a knife is less than 3 inches and
must be a non-locking folding blade.
that's incorrect though, the UK law states:
The laws about buying and carrying a knife depend on the type of
knife, your age and your circumstances.
Basic laws on knives
It is illegal to:
- sell a knife to anyone under 18 (16 to 18 year olds in Scotland can buy cutlery and kitchen knives) unless it’s a knife with a folding
blade 3 inches long (7.62 cm) or less, eg a Swiss Army knife
- carry a knife in public without good reason - unless it’s a knife with a folding blade 3 inches long (7.62 cm) or less
- carry, buy or sell any type of banned knife
- use any knife in a threatening way (even a legal knife, such as a Swiss Army knife)
Lock knives (knives with blades that can be locked when unfolded) are
not folding knives, and are illegal to carry in public without good
- As stated, I don't believe this would be classed as a knife
- It's certainly not on the banned list
- You have a good reason (going into the woods to cut dead wood) so even if you were pulled over (and they decided your very unknife looking item) was a knife it shouldn't be a problem.
There is a chance that in the wrong context this could be classed as an offensive weapon (for example, if you're in an inner london housing estate hanging out with a gang with this concealed in a bag then the police may well think that you're up to no good). If you're in a rural area on your way to the woods carrying a saw then no police constable in his right mind would class this as an offensive weapon and even if they did I would like to see them make that stand up in court.