An instrument creating an enduring power of attorney must be executed—
(a) by—
(i) the principal signing the instrument; or
(ii) a person, who is eligible to do so under section 34, signing the instrument in the presence of and at the direction of the principal; and
(b) by 2 persons—
(i) who are present and who witness the signing of the instrument; and
(ii) who sign and date the instrument in the presence of the principal and in the presence of each other; and
(iii) who certify in writing in the instrument in the manner required by section 36.