While Londoners scurried from building to building seeking shade on another baking hot day this week, one man paused in the shadow of the Royal Courts of Justice.

The leader of Oxfordshire county council, Tim Bearder, was not only satisfied in the shade of the court’s gothic towers. He had just won a landmark legal victory.

On the face of it, the case was an argument about local council permissions. But such is the febrile nature of British politics, the proceedings took on a whole new importance – one which strikes to the heart of raging debate in England over its most recognisable icon: the national flag.

The court, one of the most important in England and Wales, had decided that hanging the English flag from lampposts without the council’s permission should not be allowed.

Activists who have been hanging the flag of St George along roadsides in what has been a growing display of nationalist sentiment, were dismayed, accusing politicians such Bearder of “not liking the flag of their country”.

Bearder, a public servant and proud Englishman, was delighted.

“We’ve secured the first ever injunction [of its kind] in the country and this will serve as a blueprint for other councils wishing to stop this irresponsible behaviour,” he said.

Tensions have been growing between the Raise the Colours group and the council since the former began its “nationwide campaign to cover Britain in flags” last summer.

The phenomenon began in Birmingham, with flags of St George and union jacks appearing on lampposts, roads and roundabouts, before spreading across the west Midlands and beyond - from Worcester to Greater Manchester and Newcastle in the north.

Raise The Colours states on its website that it is a grassroots movement that has “grown into a campaign to cover Britain in symbols of unity and patriotism”. Others have accused the group of spreading anti-immigration rhetoric and vigilantism – claims it has previously denied.

Oxfordshire council became aware of the flags in the county in August last year, and initially decided against taking action in the hope the movement would eventually “blow over”, Bearder said. “We didn’t want to give them that fuel so we just took a very light touch approach.”

As the campaign continued, however, that approach was no longer feasibleand the council decided to take the flags down.

“They [were] doing it in very dangerous situations on busy roundabouts with just a ladder,” he said. “As a highways authority, we have a legal responsibility to maintain a safe highways network.”

In its claim to the high court, the council said contractors removing flags had been met “with hostility and obstruction” from people associated with Raise the Colours, including two incidents where they were “obstructed, harassed and intimidated”.

It also referred to other incidents where “vehicles were used to prevent the contractors from operating a working platform” and contractors being followed to their yard.

Bearder said such episodes had led to staff not turning up for work or refusing to take down the flags. Those who did would do so at night while wearing balaclavas and using unmarked vans, in an effort to avoid confrontations with the group, Bearder said.

“They’d feel very nervous about doing it because they live in this community and they’d be there getting this kind of abuse,” he said.

The council issued a formal legal notice to Raise the Colours in March that required the group to stop installing unauthorised flags, calling it an “act of intimidation and division” and saying residents reported “feeling distressed, unwelcome and unsafe in their own neighbourhoods”. The council sent further pre-action letters to named individuals in May.

Bearder said the council had decided to pursue an injunction because it was the most cost-effective method of stopping the campaign. The local authority had spent about £50,000 on removing the flags, he said.

“We do get the challenge: ‘Why are you spending any money taking down flags when you should be fixing potholes?,” he said. “That’s what we’d rather be doing … This council is facing £24m of cuts this year. We don’t want to be spending money on legal action to prevent people doing illegal things.”

At the culmination of the showdown in London, Bearder and his Liberal Democrat-led council were vindicated. Four people associated with Raise the Colours agreed to stop hoisting England flags on lampposts after the judge granted the council a high court injunction.

Ryan Bridge, Trudy Wells and Ben Cullen also told the court they would not encourage others to raise flags from public infrastructure or impede staff from taking them down.

No sooner had the matter been settled in the sober environs of the court, than the vitriolic reaction began in the media. The Reform UK MP Richard Tice accused the Liberal Democrats of hating England and patriotism, while the former Premier League manager, Harry Redknapp, criticised “stupid councillors who [have] idiotic opinions”.

Bearder said he had received hundreds of emails and messages online since Tuesday, some abusive and threatening, which he attributed to misinformation that the council had sought a wholesale ban on flying flags in the county.

“It’s fairly astonishing the level of abuse and vitriol,” he said. “What we’ve said is we’re banning any objects from being attached to lampposts and other highways infrastructure.

“We are very explicitly not about banning people who want to fly the flag on their own private property. We fly the flag on our own council buildings and we’re very proud to do so,” he said, adding that he has also displayed the flag of St George at his home in support of England at the World Cup.

“It’s not a culture war, which is what they’re constantly trying to make it into. It’s not that we’re some kind of Liberal Democrat, woke-run council who are trying to ban the flag,” he said.

“We’re very explicitly trying to maintain a neutral space for our residents, a safe space for our residents so that we can all travel around the county freely without intimidation, or the risk of a flag flapping onto your windscreen or lamppost falling in front of you.”

Bearder said he was “proud to be leading the way in this space” and was aware of other councils who were considering similar action.

“I know that lots of councillors have been in contact with us, watching us very closely to see how successful we were,” he said.

“Even if the high court judge had not agreed, we would have tried, because we didn’t have any other option. We had to try to demonstrate to our residents that we were doing what we could to enforce the law.”

Birmingham city council has said unauthorised flags attached to public infrastructure will be taken down and that it is “in discussions with our partners to ensure these items can be removed safely and at the appropriate time”.

A spokesperson said: “The council will consider all options available to enable this to happen and to protect our communities and our assets up to and including legal action.”

Raise the Colours has been contacted for comment.

In a video posted on Tuesday on the Raise the Colours social media, Bridge said: “We haven’t had the result we wanted today, because we want to be able to put up flags of our country wherever we like … We got a complete blanket ban on all flags, it wasn’t just our flag of our country – the union and the St George – but we also got a ban on flags from other countries.”

In an interview after the high court hearing, Bridge said the injunction was “horrendous” and he was being shut down.

He also described Oxford as “completely finished”.

“These people have got too much time on their hands and they despise the likes of us,” he said. “They don’t like the flag of their country. They believe in open borders. They’re the problem.”