I am afraid you have completely mixed up the difference between the board of trustees and the employees that form the management organisation that runs the national trust. The board of trustees are not employees of the national trust they provide an overview function and goven the dirdction of the trust, they do not provide the management of the trust.
The next section covers staff costs, copied below
The numbers of full-time/regular employees whose pay and taxable benefits exceed £60,000 fell within the following bands:
£170,000 – £179,999 1
£140,000 – £149,999 1
£130,000 – £139,999 0
£110,000 – £119,999 2
£100,000 – £109,999 2
£90,000 – £99,999 1
£80,000 – £89,999 7
£70,000 – £79,999 17
£60,000 – £69,999 19
Thus, for the National Trust to attact and retain appropriate employess they do have to offer a circa £200k salary for the top person in the organisation.
PeterF