FTSE 100 help - why can i still trade this after hours?

Im trying to understand why i can trade on the FTSE 100 out of trading hours but i cant find an answer anywhere

Many thanks

https://www.financial-spread-betting.com/24-hours-trading.html

Thanks Nick!
So they still offer the FTSE 100 out of hours but they work out the price from other instruments?? Is it best to stay away from this then and keep it to trading hours?!

@matt588812 Almost every single CFD provider bases their Indices on index futures as spot/cash Indices aren’t actually tradeable. The price is based on ICE’s FTSE 100 Index Future https://www.theice.com/products/38716764/FTSE-100-Index-Future