After each one of them breaking through to the other's side of the pen several times in an hour, I gave up and put them back in together (ish). I've left the divider up in the pen but have left room for them to be able to walk around it at each side, so they can still have time apart. www.mumsnet.com/68927.Ups
It's a sort of halfway house to getting them back together full-time. So far, no bloodshed, but it's early days.
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