20. (1) Where payment on account of a debt or of interest on a legacy is made before the expiration of the prescribed period by the person liable to pay the debt or legacy, or by his duly authorized agent, a fresh period of limitation shall be computed from the time when the payment was made:Provided that, save in the case of a payment of interest made before the 1st day of January, 1928, an acknowledgment of the payment appears in the handwriting of, or in a writing signed by the person making the payment.