True to form, this was found in woodland area, I think it hardy enough to fend for itself, whilst also living side by side crowded wildlife.

Purple Loosestrife (Lythrum salicaria), perhaps.

I agree with purple loosestrife suggestion. Though I cannot specify details, it's got that color and that messy flower look.

Pics Lythrum salicifolia.
Garden centres here sell named ones such as Lythrum salicifoliaDropmore Purple,Lythrum salicifoliaBlush etc.
Grows best where soil is moist

Regarded as a problem plant in North America, but as you are in UK that may not apply to your situation.

I think you meant Purple Loosestrife (Lythrum salicaria)

@Silversurfer: The soil likely will be moist as it's right next next to public ponds.

Here, by the perimeter, the Swans and Ducks will come up to feed if you have bread.

Calif_Sue said: I think you meant Purple Loosestrife (Lythrum salicaria)

I am so sorry ..my error.
No idea why I made that mistake!
I did indeed mean Lythrum salicaria ...common name Purple Loosestrife.

Silversurfer said: I am so sorry ..my error.
No idea why I made that mistake!
I did indeed mean Lythrum salicaria ...common name Purple Loosestrife.

I was curious about that and found that some Google results primarily from the UK do use the name L. salicifolia, as in:

https://mooreandmooreplants.co...

and

https://www.bents.co.uk/p/lyth...

Yet it doesn't appear to be a valid species name or synonym.