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The art deco HQ of the Royal Institute of British Architects was a controversial addition to the Georgian terraces of Portland Place in 1934, but these days it is just the sort of place Prince Charles might feel at home.

Its magnificent Florence Hall, with its floor-to-ceiling windows, etched glass doors and patterned marble floor, is to be the backdrop for a reception to celebrate the institute’s 175th birthday next month, at which the Prince of Wales is to speak.

Alas, though the surroundings may be grand (and, in the prince’s terms, reassuringly traditional), the atmosphere promises to be far from convivial. For, 25 years after his speech denouncing a planned modernist extension to the National Gallery in Trafalgar Square as “a carbuncle on the face of a much-loved and elegant friend”, the prince is crossing swords with the architectural establishment — again.

The 60-year-old prince was invited to speak at next month’s event, according to Sunand Prasad, Riba’s president, as “a gesture of reconciliation”. The gesture stands, but reconciliation looks increasingly unlikely.

Two weeks ago The Sunday Times revealed that after privately approaching its Qatari developers, Charles was close to scuppering plans for a huge Lord Rogers-designed cluster of glass and steel towers to be built opposite the Royal hospital, Chelsea, home to generations of scarlet-clad Chelsea pensioners.

Incensed that their old enemy should be on the prowl again, a group of Pritzker prize winners — the architectural equivalent of the Nobel prize — including Lord Foster, Zaha Hadid and Renzo Piano, wrote to The Sunday Times last week accusing Charles of trying to “skew the open and democratic planning process”.

Now a group of traditionalist architects, including Robert Adam, one of the prince’s favourites, has taken up cudgels against the modernists, and buttresses are flying in all directions. The irony is that in recent years, since Charles latched onto climate change, he and the modernists — concerned that their steel and glass boxes be eco-friendly — have found a lot of common ground.

The prince’s speech next month was supposed to acknowledge that and bury their differences.

“What might have been a receptive audience is now very likely to be hostile,” says Hugh Pearman, architecture critic and editor of the Riba Journal.

There’s no doubt that the prince remains the people’s champion as far as architecture is concerned. Naturally conservative, the British public tends to like designs with a traditional flavour: of the many readers who have written in about the row, some 80% back the prince.

But, given that Charles — almost — had a new generation of architects on his side, there is a question over the wisdom of interfering in such a high-profile development. Is it a triumph for common sense or has Charles, as one Riba insider suggests, simply shot himself in the foot?

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