Update …

IG replied on 8 Oct 18, seems that  … although the date on the System I advised them about states 19 Apr 18 … IG are saying that the accumulated profit dates back to 19 Apr 17.

Glad I wrote above as I now see that they have almost certainly made a typo  as both say 17 Apr and they just typed 17 instead of 18?

So my conclusion is that IG do not acknowledge that there is any Issue as described in this Thread!? So it seems the only way to solve the nonsense Profit showing on several of my Systems is to Stop System, Copy the Code into Code Backtest and then start it again in Demo Auto-Trading and so lose all the Performance History!? (actually I put a note re History in the Notes section, but unfortunately you can’t see this anyway in the Auto-Trading window! )

Oh well, this pushes Live Trading even further away for me!

Here is the full answer from IG

The profit showing as £24.7K should be a representation of the profit/loss of this strategy since the first time you used it (appears to have been 19-Apr-2017). You would need to delete it and re-create the Strategy to remove this balance as stopping and starting will continue to add P/L to this total.
I suggest copying the current code and pasting this into a new one.