No interactions present.
Looks like some kind of spinach or beet, perhaps a mixed planting.
... the flowering stem of a chard.
Is based on the assumption it's a native species; but the area Ms Baughan is looking at was planted with all sorts of exotics when I was there. That's rather a long time ago, though!
Nothing like Persicaria maculosa!!
the garden is growing all sorts of vegetables and herbs so the beetroot or chard are the best bets.
After looking at this plant again I think it may be chard-as suggested.
Lat/Lng: 52.3, -2.4
OS grid ref: SO7874