This was discussed not long ago and I think the consensus was metre high coarse mesh with an electric line set inboard of it to stop them digging up underneath. You can buy extended insulators to screw into the same posts as the fence. Here they just use two solid steel electric lines set at 8" and 15" on short posts about 2 metres apart. You will need a decent energiser, so 2.0 Joules or so. Don't forget a solid gate.
Do you have enough time to do the fencing or will you need to put them in a barn for a while?