Litigating on a group action worth in the region of £5bn is never likely to be easy, but Tuesday’s hearing (the full write-up is here) before the Court of Appeal was a particularly bruising experience for the lawyers involved.

In the Brazil dam case Mariana, Master of the rolls Sir Geoffrey Vos agreed to double the two hours allocated to the application (which was complicated enough, being an application to appeal a decision to refuse permission to appeal the strike-out decision). But that was about as far as his patience would stretch, as he proceeded to grill both lead advocates on the merits of their case.

Things should have been straightforward for the claimants’ QC Graham Dunning after Sir Geoffrey had even said he would have granted permission to appeal the strike-out. But as the hearing went on, it became clear this did not mean the appellants would have a clear ride.

At one point, the judge interrupted Dunning to ask: ‘Do you think you could be accused of having complicated your case rather?’

The advocate responded that there was ‘some fairness’ in such an observation, but the judge wasn’t finished. ‘Your grounds of appeal are terribly convoluted,’ he noted. ‘It is absolutely imperative in setting out grounds of appeal that you do thinking before you do writing. All the writing here was done first and thinking done later.’ Ouch.

Sir Geoffrey was no more forgiving when Charles Gibson QC spoke for the defendants. Having been peppered with suggestions the case was ‘impossible to manage’ and ‘utter chaos’, the judge said: ‘One of the problems with this case is the use of extreme adjectives at every turn. It just raises the temperature without any intellectual insight.’

Possibly Sir Geoffrey thought he had been a little harsh. In his final remarks, he went out of his way to praise both barristers for the clarity of their arguments, noting: 'We have got to the bottom of the difference that lies between you'. 

Judgment was reserved.