Equity and Trust

‘The beneficiary principle has hampered the development of trusts law in England and Wales for over two centuries; it is too rigid and enforced far too strictly. Until the rules surrounding it are relaxed then there cannot be any flexibility with respect to private purpose trusts in this jurisdiction.’
Discuss this statement.

i am in my second year undergraduate degree, so therefore need an excellent answer to the above question. thoroughly discussed. (i need oscola referencing method).