Optimist wrote:

Policy should be to get the hundreds of thousands of empty homes
back into use, rather than consuming more countryside.

Very laudable in theory. In practice many of those empty properties
are in areas no one wants to live.

Like central London, you mean? There are loads of houses in the most
expensive areas which have been boarded up and the sanitary fixtures
destroyed to make them uninhabitable.

Land Valuation Taxation would sort that out. Full tax is paid only on the
LAND's value. The building is not taken into account - it could be an empty
plot. They soon get the building profitable. The laws relating to land
were forced through by landed vested interest over the centuries.