I'm unable to see your image, but if the leak is at a welded joint as opposed to a screwed joint, then there is nothing you can do other than replace the towel rail.
As only two years old, I would be thinking in terms of making sure the system is OK, and has inhibitor added.
Thanks - we had some radiators replaced recently and inhibitor was added at that point, though in the two years preceding there was none. The leak is at a welded joint - must've corroded through? Thanks for your help.
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