Although the SFO has had a somewhat chequered history since being created in 1988, it is widely believed that the prosecutor-led approach to tackling large and complex fraud, which the UK imported from the US, has proved more effective in recent years.

BBC: SFO saved by cabinet revolt

It is thought the moths were brought into the UK on trees imported from Europe for a landscape project.

BBC: Pangbourne plan to eradicate oak processionary moth

MPs have backed campaigns by supermarket chains including Asda and Tesco to end restrictions on the 'grey market' where genuine trademarked goods are imported from abroad to be sold within the UK at reduced prices.

BBC: News | UK Politics | MPs back cheaper designer goods

The caterpillars are likely to have come to the UK as eggs on imported trees from Europe.

BBC: Oak processionary caterpillar

Prestwich says French tarragon, which is the type largely imported to and grown in the UK, is a slow-growing plant, which can only be grown from cuttings, not seeds.

BBC: Who, What, Why: Where has all the tarragon gone?