13Sections 21 to 24 do not apply in relation to expenditure—
(a)incurred before 30th November 1993;
(b)incurred before 6th April 1996 in pursuance of a contract entered into before 30th November 1993; or
(c)incurred before 6th April 1996 in pursuance of a contract entered into on or after 30th November 1993 for the purpose of securing that obligations under a contract entered into before 30th November 1993 are complied with.