Can a High Court Writ be cancelled?

[mcflurry]

Watching one of the High Court Sheriff programmes the other day, the debtor called his solicitor to try and set aside the Judgement.
With a County Court judgement, the debtor could pay £250, fill out a (N244?) form and have the Judgement set aside, if they were unaware of the case. However, the solicitor and bailiff were arguing that the case had been heard and so couldn't be set aside.
Who was correct please?

[mcflurry]

Thank you