1. The plaintiffs in the suit are the appellants.

2. The facts relevant for adjudication of the questions raised in the second appeal are the following:

The plaintiffs are husband and wife. The plaint schedule property belongs to the plaintiffs absolutely and they are in possession of the same. The plaint schedule property forms part of a cluster of paddy fields (padasekharam) measuring approximately 360 acres and managed by a Committee. The first defendant in the suit is the Committee and the remaining defendants are its office bearers elected from time to time. Three motor pumps are installed at different places of the paddy fields by the Committee for draining out the water collected in the paddy fields and one of the said motor pumps is installed in the plaint schedule property which being one situated adjoining the river to which water is being drained out. It has been a practice to catch the fish by keeping fishing nets at the mouth of the motor pumps installed for draining out the water from the paddy fields. The case of the plaintiffs is that the fishery being their property, they have the exclusive right to catch the fish, notwithstanding the fact that the fishery is formed on account of the pumping activity undertaken by the Committee. It is also their case that both the plaintiffs as also the Committee were under the mistaken impression that the right to catch fish from the mouth of the motor pumps vests with the Committee and consequently, they have agreed to pay an yearly sum to the Committee to enable them to catch fish from their own property in terms of an agreement. According to the plaintiffs, the agreement entered into by them with the Committee being one vitiated by a common mistake is void. On the said case, the plaintiffs sought a declaration that they have the exclusive right to catch fish from the water that is drained out into their property on account of the pumping activity undertaken by the Committee. They have also claimed a decree of permanent prohibitory injunction restraining the defendants from interfering with their fishing activity and also a decree for return of the amounts paid to the Committee in terms of the agreement.

3. The defendants contested the suit. The stand taken by the defendants is that the owners of the paddy fields have a customary right over the fishery formed on account of the pumping activity and the plaintiffs cannot claim exclusive right over the same merely for the reason that the fishery is formed in their property.

4. The trial court found that the plaintiffs have the exclusive right over the fishery, though the fishery is formed on account of the pumping activity undertaken by the Committee and consequently, decreed the suit. The first defendant challenged the decision of the trial court in appeal. The appellate court though confirmed the finding of the trial court that the plaintiffs have absolute right over the fishery, reversed the decision of the trial court and dismissed the suit holding that the plaintiffs having entered into Ext.A3 agreement with the first defendant, are not entitled to the decree sought for in the suit. The plaintiffs, who are aggrieved by the decision of the appellate Court, have thus come up in the second appeal.

5. Heard the learned counsel for the appellants.

6. The learned counsel for the appellants contended that Ext.A3 agreement is one entered into by the parties under the mistaken belief that the first defendant has the exclusive right over the fishery. According to the learned counsel, insofar as it is found that the first defendant has no rights whatsoever over the fishery and the plaintiffs have the exclusive right over the same, the agreement is void under Section 20 of the Indian Contract Act, 1872. The submission of the learned counsel, in the circumstances, is that the appellate court ought not to have interfered with the decision of the trial court.

7. After hearing the learned counsel for the appellants, the following subs