The trustees shall hold the capital and income of the trust fund upon trust to apply the income , and all or such part or parts of the capitals , at such time or times and in such manner to or for the benefit of such exclusively charitable objects and purposes in any part of the world as the trustees may in their discretion think fit and in particular the provision of, or assistance in the provision of, education or welfare for children or young persons either for the benefit of the general public or for the benefit of those who, by reason of their youth , infirmity or disablement , poverty or social and economic circumstances, have a need for such facilities.