Rent income earned by a trust from let out of property

On what basis will the rental income earned by a charitable trust from let out of a spare flat/property be taxable , under which section will such rental income be charged to tax for the Trust ?
Will charging section 24 (i.e. taxation of house property) apply ? or will it be considered in the total income earned by the trust from which the ad hoc exemption of 15 is be reduced ?
(Renting is not considered as an object of the trust . It has let simply let out a spare flat)