Can anyone explain the discrepancy here? The ‘Performance Calculation’ screen shows a realized capital gain of -4949892… but the associated buy/sell transactions are for £50/£51k?
The calculation is correct, just the data is wrong. Specifically, the security supposedly was worth £95 on 2022-11-17 (when in reality it was more likely £0.95). So, according to the data, the position was worth five millions at that time, and you suffered a huge loss when you sold it for only fifty thousand later.
Thanks @chirlu, I’d missed that the performance calculation was over 1 year and hence why it would be relying on pricing data rather than buy/sell prices. Tracked it down to a GBP/GBX inconsistency in the sourced quotes as you mentioned.