NT stated at the time that the monuments would have been used anyway (via computer enhancement) so they thought they might as well cash in (my words - their sentiment). They also said that they needed to constantly review ways of generating income to help fund the 'preservation' of the sites in their care and gave the impression that this was one route they had decided to take.

In the previous thread, re: Uffington, there was a response from NT posted (I think) with this statement in it.