Subject to subsection (2), a solicitor may make an agreement in writing with his client as to his remuneration in respect of any contentious business done, or to be done, by him (in this Act referred to as a "contentious business agreement") providing that he shall be remunerated by a gross sum or by reference to an hourly rate, or by a salary, or otherwise, and whether at a higher or lower rate than that at which he would otherwise have been entitled to be remunerated.
Nothing in this section or in sections 60 to 63 shall give validity to—
(a) any purchase by a solicitor of the interest, or any part of the interest, of his client in any action, suit or other contentious proceeding; or
(b) any agreement by which a solicitor retained or employed to prosecute any action, suit or other contentious proceeding, stipulates for payment only in the event of success in that action, suit or proceeding; or
(c) any disposition, contract, settlement, conveyance, delivery, dealing or transfer which under the law relating to bankruptcy is invalid against a trustee or creditor in any bankruptcy or composition.