Section 19

Statements made by persons whose position or liability it is necessary to prove as against any party to the suit are admissions if the statements would be relevant as against those persons in relation to the position or liability in a suit brought by or against them, and if they are made whilst the person making them occupies that position or is subject to that liability.

A undertakes to collect rents for B.

B sues A for not collecting rent due from C to B.

A denies that rent was due from C to B.

A statement by C that he owed B rent is an admission and is a relevant fact, as against A if A denies that C did owe rent to B.