HALTON BOROUGH COUNCIL V SECRETARY OF STATE FOR HOUSING, COMMUNITIES AND LOCAL GOVERNMENT [2025] EWCA Civ 1566

A costs award against a council whose expert conceded key points under cross-examination has been quashed. There is no “normal procedural requirement” to test expert evidence, and parties cannot be expected to second-guess their experts.

• A party’s reliance on its expert evidence is not unreasonable merely because it is later undermined in cross-examination. For such reliance to be unreasonable, there typically needs to be a trigger, such as an obvious flaw in the evidence or a clear challenge from the opposing side that should have caused the party to doubt its expert’s views.
• There is no normal procedural requirement for a party to test or guarantee that its expert’s evidence will withstand cross-examination. An instructing party is entitled to rely on the independent expert it has engaged, and the subsequent failure of that evidence under scrutiny does not, without more, constitute unreasonable conduct.
• Withdrawing support for a case following a material change in an expert witness’s evidence during proceedings is for good reason and is not, of itself, unreasonable behaviour justifying a costs award.
• A finding of unreasonable conduct based on a failure to comply with procedural requirements must identify the specific requirement that was breached. A general assertion that a party should have better prepared its case is insufficient if it does not correspond to a recognised rule, direction, or established normal procedural requirement.
• A costs decision based on contradictory reasoning—such as accepting a party acted due to new evidence while finding there was no material change in evidence—contains a demonstrable logical flaw and is liable to be quashed for irrationality.