Re: Severe Poisonous Plant - beware!
Good grief no.
According to the RHS, it was first recorded here in 1828 I think.
Have a look at this from their website:
The giant hogweeds were introduced into Britain and Europe from the Caucasus Mountains in the nineteenth century. The earliest documented reference to their introduction into Britain that has been traced is from the Royal Botanic Gardens Kew Seed List of 1817 where giant hogweed, under the name of Heracleum giganteum was listed among seeds supplied to Kew by the Russian Gorenki Botanic Gardens. They were soon introduced into the horticultural trade and being aesthetically impressive plants, were widely planted in ornamental gardens throughout Britain. Unfortunately they quickly escaped from cultivation with the first naturalised (‘wild’) population recorded in Cambridgeshire in 1828, and are now widely naturalised as invasive species throughout much of Britain and Europe.
When controlling giant hogweed always wear gloves, cover your arms and legs, and ideally wear a face mask when working on or near it. Cut plant debris, contaminated clothing and tools are potentially hazardous too. Wash any skin that comes in contact with the plant immediately. Ensure that contractors working on your land are aware of the risks and competent to deal with this weed.