An example of fasciation
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I think this is a case of fasciation (a mutation in the meristematic cells) that can be brought about by a bacterial infection, mite or insect attack, or chemical or mechanical damage.
I did say it was fasciation - the reason why I added the photo, as I haven't seen many posted on iSpot. Incidentally I have now seen this two years running in the same general spot.
Sorry - did not see your comment.
It might be late frost or some kind of Gall fungus. I first noticed in in the 1970s and have not seen it for since.
Lat/Lng: 50.8507, -0.1218
OS grid ref: TQ323073