Interesting that you keep saying this.
Under Section 14(1) WCA 1981 it is an either way offence to release into the wild, or to allow the escape of, any animal which is not ordinarily resident, or a regular visitor to, Great Britain in a wild state: or which is included in Part 1 of Schedule 9. [...]
In either instance, however, it is a defence under section 14(3) that the accused took all reasonable steps and exercised all due diligence to avoid committing the offence. (
source)
I'm no lawyer, admittedly, but this sounds like intent does, in fact, come into it - there is an accidental escape where an animal
unexpectedly went against its specific training and did not respond to the safeguards put in place (ie. food or devices - such as clickers or whistles - carried by the keepers as contingency for this exact scenario)... and then there is an "accidental escape" which occured entirely due to negligence, such as zoos not maintaining their enclosures to the degree required to them by law.
You should consider the risk of escape when you are considering using any nonnative animals in demonstrations outside of a secure enclosure. You should however ensure that these animals cannot escape into the wider environment
and that you have contingency plans in place that can be enacted in the event of animals escaping into the wild. (
source)
ZSL
did have contingency plans in place in this instance: the animals in question will have been microchipped and / or ringed to aid with identification, will have recieved specific training to facilitate this free-flying behaviour (with evidence of a structured, science-based training programme being carried out), and will have procedures laid out for if animals do not return as expected (again, with evidence that the keepers were ready and prepared to enact these procedures at the point at which they took the birds out of the enclosure).
For anybody who is interested, there is a specific exemption in the Wildlife and Countryside Act for free-flying birds of prey:
In principle, we would not regard the long-standing and traditional practice of falconry as amounting to the commission of the offence.
Such birds are clearly expected to return and competently done, there is no intention to allow the birds their freedom to establish in the wild. The legislation provides a defence if the accused can prove that all reasonable steps have been taken, and all due diligence has been exercised, in order to avoid committing the offence.
Thus, the competence of the handler and the degree to which the bird has been properly trained will be relevant considerations. The release of surplus or unwanted birds, with no intention of retrieval, would constitute the offence. (
source)
("Intention" is mentioned twice in this paragraph, by the way)
