Twycross made a wise husbandry decision to restrain their cows and remove the calves as soon as they were born until the mothers had calmed down. They almost certainly would have kicked the calves to death had this not been done. This reflects the absolute lack of reference point that the first-time mothers had, given the age at which they arrived at Twycross, and I think this is part of the issue, that to calve successfully required a huge amount of intervention by the staff. It was however a great success within the context of a captive birth situation.
In the UK, I don't think Longleat, Belfast, Edinburgh (while they still had them), Twycross or Blackpool have been great examples of Gorilla husbandry in recent years, although admittedly Longleat made the best situation they could with two ex-circus animals. Jersey and the John Aspinall parks have always been good examples of how to keep this species, and Chessington has done well with less room but a good group dynamic until recently, my point was not that gorillas are not suited to captivity, more that it is possible to have long-lived individuals in less-than-ideal social groupings or enclosures, and that longevity alone is not a justification for the conditions the animal is kept in.