A hybrid finch? If so which species are involved?

Received this image via ringers working in Bristol/Chew area (forwarded by Lydon Roberts). This odd looking bird was apparently caught last autumn and has been seen/re-trapped since. Nobody is quite certain but it is assumed most likely to be Greenfinch x Goldfinch.
Whether it is the result of a natural occurrence or a deliberate experimental crossing by someone, nobody knows.

Perhaps there is more in those sunflower seeds or peanuts put out at feeding stations than we realise! Watch out, one might turn up in your garden!