20 minutes from London you are looking at about 5-10m per hectare and as mentioned good luck finding an empty square meter let alone a hectare.
https://www.rightmove.co.uk/commercial-property-for-sale/pro...
Once close to a HS2 station yes it would be £5m a hectare
Nice to know we explicitly provide for land owners to extract rent even when they don't own the land any more.