From "gardening experts" on twitter
I've currently got a two-way tie on what your plant could be: Member of Lamiaceae family, most likely Clary sage (Salvia sclarea) Foxglove (Digitalis purpurea).
Warning, Foxglove - Noteworthy Characteristics: Plant leaves are a source of the drug digitalis and are highly poisonous.
If it's Clary sage, the leaves should smell aromatic when crushed & the face of them should feel hairy (furry) to the touch.
If it's Foxglove the leaves will feel soft to the touch.
The "gardening experts" on twitter all agree with, if you let it flower it will make identification 100%.
gardening.stackexchange.com/users/394/Mike Perry
The plant in your photos has leaves which seem identical to those of Green Alkanet ( Pentaglossis sempervirens ) which has hairy (furry) basal leaves with purplish stalks: Perennial, member of the Boraginaceae Family.
Native to south-west France, and the Iberian Peninsula, but is now naturalised throughout the British Isles.
Prefers shaded, damp areas.
It was brought here for the red dye which can be extracted from the roots, but escaped from cultivation.
The leaves are rough and covered with hairs.
The lower leaves in the basal rosette have no stalks, but the upper ones on the stems have stalks.
The stems can reach up to 75 cm.
The bright blue, forget-me-not-like flowers appear from April to July and arise from the upper leaf axils in clusters with two small leaves behind them.
They are edible and are sometimes used to decorate salads.
Green Alkanet
There are quite a few of these plants growing under hedgerows, by the roadside and in neglected gardens in Manchester, where I live (see photos), and they have just finished flowering.
As Green Alkanet has basal leaves that are almost indistinguishable from those of the Foxglove, we shan't know which of the two (if either)
your plant is, until it produces flowers; if it hasn't already done so, it is likely to be a foxglove, since this is a biennial.
If it has now flowered, perhaps you could post a photo, so that we can confirm its identity.
gardening.stackexchange.com/users/136/Mancuniensis
It is worth considering that it might also be Comfrey .
Here's are a couple of images of comfrey from Wikipedia that show the similarity of the leaves with your plant.
gardening.stackexchange.com/users/1074/greenhorn
Its Digitalis (foxglove).
It doesn't have the hairiness of one of the Borage family, although its easy to confuse the two before they flower - the way to tell is by touch.
Borage feels unpleasant to handle, Foxglove doesn't, being soft.
I suspect it was planted deliberately - it is surrounded by Lamium maculatum and the blue flower appears to be Tradescantia - all these are used in the UK for shade planting.
gardening.stackexchange.com/users/1380/Bamboo
It looks like Sea Holly to me - Eryngium (perhaps Eryngium Planum?)
gardening.stackexchange.com/users/773/Janetteh
Does anyone have any idea what this is? It looks too substantial to be a weed
What is this large furry leafed plant with purple stalks, found in the UK?
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gardening.stackexchange.com/questions/1467
gardening.stackexchange.com/users/54/Dan
It could either be clary sage, foxglove, green alkanet, comfrey or sea holly. Your plant is most likely to by Clary sage  (Salvia sclarea)  or Foxglove  (Digitalis purpurea).   Other possibilities are Green Alkanet ( Pentaglossis sempervirens ).  It is worth considering that it might also be  Comfrey  or Sea Holly.
Your plant is most likely to by Clary sage  (Salvia sclarea)  or Foxglove  (Digitalis purpurea).   Other possibilities are Green Alkanet ( Pentaglossis sempervirens ).  It is worth considering that it might also be  Comfrey  or Sea Holly.