Every Little Bit Helps
Ten years ago the major museums and galleries removed the entry charges for permanent exhibitions.  In London alone there are 46m visitors each year to these establishments. If a charge of £1/head were introduced the exchequer could pocket £46m/year without causing hardship to anyone. Perhaps even £2 at peak times. For the cost of a few turnstiles the museums woould benefit considerably. If they used the Oyster card it could be made even  more painless.
It is not much of a vote winner though, is it?