All 57 works must remain free to view and never be sold, according to wishes of late owner Sir Denis Mahon

A collection of 57 old masters worth around £100m – some bought for as little as £100 apiece in the mid-20th century – are to be formally given to the nation, with strings attached. If any attempt is made by the host museum to charge for admission; or any item from their collection is put up for sale, the Art Fund, the charity that is donating them, can take them back.

The conditions attached to the donation of the works, among them paintings by Guercino, Guido Reni and Luca Giordano, are in line with the wishes of the collector who amassed them: art historian Sir Denis Mahon, who died in 2011, aged 100.

The conditions seem especially resonant now, as museums suffer funding cuts and charging for admission is again being reluctantly considered in some quarters. There are also increasing examples of public bodies selling artworks to help plug financial holes – as with the attempt by Tower Hamlets council in London to sell a Henry Moore sculpture that the artist had intended for public display.

According to Stephen Deuchar, chief executive of the Art Fund, the conditions "keep up the pressure for governments to do the right thing by museums and galleries".