Arron Banks posted "Welsh lad?" on X in response to a Plaid Cymru video fronted by a black community organiser.
Banks wrote "Welsh lad?" in response to a video from a black Plaid Cymru activist.
Former UKIP donor stands as Reform's mayoral candidate for the West of England.
The long-running dispute between the pair centred on a talk Ms Cadwalladr gave.
The anti-lockdown, pro-Brexit journalist finds herself at the centre of a political row - not for the first time.
The Brexit campaigner says he will "likely" appeal against the High Court judgement.
