At the allotment yesterday I suddenly saw a deer running through. I had though the problem was with muntjacs but this was much bigger. It jumped straight over the fence through the hedge and was off. I had been concerned with the fact that there was a gap in the fence, but the fence would have to be very high to prevent this.
You need pretty elaborate protection to stop deer jumping in. The Forestry Commission use six-foot high wire fences with overhanging barbed wire, which are a bugger to climb over!
I've read that a double 1.8m+ fence with a space between stops them - the space only needs to be wide enough so they can't jump both in one go - and they don't like landing in the cramped space between. The second fence mainly has to LOOK strong.
Presumably you can grow stuff in the gap between - if there's anything deer don't eat. Parsnips?
In this case I'm just quoting book-learnin - so don't take my word for it.
They might find it even more intimidating if the gap was itself divided - so it looks like they're jumping into a box - but now I'm guessing...
The cost of putting a deer proof fence around the site would be prohibitive. There is a hawthorn hedge around some of it.
I got quite a shock when it saw me so hopefully the more people on site the fewer deer there will be.