Mediation is designed to provide parties with a confidential, efficient, and voluntary route to resolving disputes. When successful, it results in a settlement agreement that is contractually binding and may now be internationally enforceable courtesy of the Singapore Mediation Convention. Although UK courts strongly support mediation and the enforcement of mediated settlements, there are situations in which such agreements may be challenged.
This article outlines the circumstances in which a mediation settlement may be set aside, and whether a mediator can be compelled to give evidence about what occurred during the mediation.
1. In What Circumstances Can a Mediation Settlement Agreement Be Challenged in Court?
In the UK, a mediation settlement is treated as a contract, and the usual principles of contract law determine its enforceability. Courts are reluctant to interfere with agreements reached voluntarily, but a settlement may be challenged in the following circumstances:
a. Misrepresentation, Fraud or Undue Influence
If one party was induced into signing the agreement based on fraudulent statements, deliberate concealment, or improper pressure, the settlement may be voidable. Examples include:
b. Mistake
A settlement agreement may be challenged if there was:
For example, if both parties settled based on shared incorrect information about a central issue, the court may consider setting aside the agreement.
c. Lack of Capacity
If a party lacked mental capacity or legal authority at the time of signing, the settlement may be invalid. This includes situations involving:
d. Duress or Coercion
Where a party was pressured improperly—beyond normal commercial pressure—to sign, the court may intervene. Mediation is voluntary, so any evidence of threats or improper conduct undermines the validity of the agreement.
e. Breach of Procedural Requirements
If the settlement agreement was not properly executed—e.g., not signed by authorised persons, or lacking consideration—its enforceability may be questioned.
f. Illegality or Public Policy Concerns
A mediation agreement cannot stand if its terms are illegal or contrary to public policy.
g. Lack of “True Agreement”
Occasionally, disputes arise about whether a final agreement was actually reached during the mediation. If the terms were not final or merely recorded as “subject to contract,” a court may find no binding agreement existed.
2. Can the Mediator Be Called to Give Evidence in Court?
The General Rule: Mediator Testimony is Not Permitted
One of the pillars of mediation in the UK is confidentiality. Mediation is considered a safe space for open, without-prejudice discussions. As such:
Mediators are generally protected from being compelled to give evidence about anything said or done during the mediation.
What there are disputes as to the limits of this the general position is that “without prejudice” privilege attaches to mediation proceedings, preventing material from being disclosed in litigation.
Exceptions: Very Rare Circumstances
While the bar is extremely high, the court may allow a mediator to give evidence in exceptional or compelling circumstances, such as:
a. Allegations of Fraud, Criminal Conduct or Serious Misconduct
If the mediation process itself is alleged to have involved wrongdoing—for example, a party claims that a fraudulent misrepresentation was made during mediation—the court may lift confidentiality.
b. Disputes About Whether a Settlement Was Reached
If parties cannot agree on:
a judge may consider hearing from the mediator as a neutral witness. However, courts typically explore all other evidence first and avoid involving the mediator unless absolutely necessary.
c. Threats to Life, Safety or Other Exceptional Public Interests
In extremely rare circumstances, public policy may justify overriding confidentiality.
Mediators’ Contracts Usually Reinforce Confidentiality
Most mediation agreements expressly state:
Courts generally respect these contractual terms unless the interests of justice dictate otherwise.
Conclusion
While mediation settlements in the UK carry strong legal force, they are not immune from challenge. A settlement can be set aside under traditional contract grounds such as misrepresentation, mistake, duress, or lack of capacity. However, courts favour upholding agreements reached through mediation and will intervene only where there is clear justification.
As for mediator testimony, the default position is firm: mediators cannot be called as witnesses, and the confidentiality of the process is vigorously protected. Only in rare and exceptional situations will the courts consider piercing mediation confidentiality.
This combination of certainty and protection helps maintain trust in the mediation process while safeguarding fairness and justice when genuine disputes arise.