littlecrystal
I have known a burglar (when being pursued) climb over a 6ft gate, run down the garden, climb on top of the garden shed (putting his foot through the roof) and run away through the next garden which has no gate, into the next road. I have also known one, when frightened, smash down a larchlap-type fence panel to get away.
The main trick is to make your house unattractive so the burglar says "I can't be bothered... I'll burgle the house next door"
An 8-ft barrier is much more difficult to climb over, as you can't just grab the top and haul yourself up. Trellis on top of the gate or fence doesn't look bad, and it will not support a burglar so will noisily break, preferably with plenty of splinters and rusty nails. If it has a prickly old rose climbing up it, so much the better.
Most garden gates and padlocks are very frail, but you can get better ones.
Nosy neighbours are quite useful, as long as they phone the police instead of just watching.