Over the past 40 years 4,000 pairs of Bewicks have been studied and this is only the second split they have seen.
When the male bird turned up with a new partner staff feared the worst for his partner but a couple of days later his old partner returned with a new male in tow. Both pairs of swans are now over-wintering in close proximity on the lake at Slimbridge.
As for why they may have split, Julia Newth of the WWT said:
Failure to breed could be a possible reason, as they had been together for a couple of years but had never brought back a cygnet, but it is difficult to say for sure.