This is fantastic news to hear! I'm so glad the group is all back together again 
https://www.youtube.com/watch?v=RLFMUg-LcsI
I was just searching Twycross Zoo on YouTube a couple of weeks ago and came across this while I was on holiday.
So, there are 4 in that enclosure and a single "older female" in with some Guenon.
Haha! Sorry, I can be quite ignorant about these things, although I thought i'd seen more than one in there at some point."Some guenon"? Some guenon?! That's Europe's last Crowned Guenon, and very beautiful she is too.
Here's a pic I put in the gallery back in May. I'm sure it's the same baby too, but they have simply timed the press release for the holidays. The clips reflect the antics I witnessed on my last visit at the start of July.
On their Facebook there's also a short video of just one Gibbon using the outdoor space properly- it looks terrific swinging around. But is this still the exception- are the others mainly not going outside yet on a daily basis? Post 238 on this thread indicates that may still be the case, but earlier posts from three weeks ago show at least some of them have been outside. An update would be useful..
I just read on the Facebook page of Twycross zoo, that Mongo passed away yesterday. What a sad moment! I wonder what happened.
It happened when he was anaesthetised for an examination of his large throat sac, we commented how big it had got last time we saw him.