5 The Supreme Court rules, Pt 20, make extensive provision respecting the amendment for pleading. In the present case, Rules 1 and 4 of Pt 20 have particular significance. They provide, relevantly:
"1 (1) The Court may, at any stage of any proceedings, on application by any party or of its own motion, order that any document in the proceedings be amended, or that any party have leave to amend any document in the proceedings, in either case in such manner as the Court thinks fit.
[subr RSC (Rev) 1965 o 20 rr 5(1), 8(1)]
(2) All necessary amendments shall be made for the purpose of determining the real questions raised by or otherwise depending on the proceedings, or of correcting any defect or error in any proceedings, or of avoiding multiplicity of proceedings.
......
4. (1) Where any relevant period of limitation expires after the date of filing of a statement of claim and after that expiry an application is made under rule 1 for leave to amend the statement of claim by making the amendment mentioned in any subrules (3), (4) and (5), the Court may in the circumstances mentioned in that subrule make an order giving leave accordingly, notwithstanding that that period has expired.
cf RSC (Rev) 1965 0 20 r 5 (2) [subr (1) am Amendment 305: Gaz 119 of 25 October 1996 p 7127]
(2) [subr (2) rep Amendment 231: Gaz 103 of 20 October 1989 p 8670]
(3) Where there has been a mistake in the name of a party and the Court is satisfied that the mistake was not misleading nor such as to cause reasonable doubt as to the identity of the person intended to be made a party, the Court may make an order for leave to make an amendment to correct the mistake, whether or not the effect of the amendment is to substitute a new party.
cf RSC (Rev) 1965 0 20 r 5(3)
(4) Where, on or after the date of filing a statement of claim, the plaintiff is or becomes entitled to sue in any capacity, the Court may order that the plaintiff have leave to make an amendment having the effect that he sues in that capacity.
cf RSC (Rev) 1965 0 20 r 5(4)
(5) Where a plaintiff, in his statement of claim, makes a claim for relief on a cause of action arising out of any facts, the Court may order that he have leave to make an amendment having the effect of adding or substituting a new cause of action arising out of the same or substantially the same facts and a claim for relief on that new cause of action.
cf RSC (Rev) 1965 0 20 r 5(5)
(5A) An amendment made pursuant to an order made under this rule shall, unless the Court otherwise orders, relate back to the date of filing the statement of claim.
[subr (5A) insrt Amendment 231: Gaz 103 of 20 October 1989 p 8670]
(6) This rule has effect in relation to a summons as it has effect in relation to a statement of claim.
[subr (6) am Amendment 19: Gaz 110 of 20 October 1972 p 4133]
(7) This rules does not limit the powers of the Court under rule 1. [subr (7) insrt Amendment 53: Gaz 160 of 5 December 1975 p 5071]"
6 The Master's decision rests essentially upon the following reasoning:
1. It is "borderline " whether these amendments arise out of substantially the same facts.