Yet another tax consultation paper has been published. As part of its big philanthropy drive, the government wants to encourage gifts to the nation of pre-eminent works of art. In return for their generosity donors will receive a reduction in their tax liability of 25 percent of the agreed value of the object donated.

So how will it work? If somebody wants to give a work of art to the nation, a panel of experts will first decide if it is of sufficient quality. If it is, they will agree a value. If the value is, say, £100,000, the donor will be able to take £25,000 off their tax bill for that year. Although the donor can...