ok useful to know this Grahal.

I use IG as broker and I have noticed that they do widen spreads accordingly as the underlying market vol changes drastically as it has been over last few weeks. That being said however whatever the spread is at any point in time, I would expect it to be reflected to PRT live instantaneously as people can trade of PRT directly so it cant be that IG live has one price and PRT live has another.

However if I understand you correctly you are saying that under high vol times the Forward test DEMO prices may not get updated with the latest spreads at the same time as PRT live. Is that correct? If demo doesn’t get updated at the same time however as PRT live, then why would there be difference between FT Demo and Backtest as backtest prices you mentioned are with fixed spread etc..