It was probably the pink unicorn glove puppet that did it. While architects may be used to tough negotiations with local authorities, having their planning applications mocked by a soft toy named “Mr Grunwald” seems to have proved the final straw for many of Bristol’s most eminent practitioners.

David Martyn, who works for Bristol council and describes himself as a “guardian of civic virtue”, has been accused of stifling development with an overzealous approach to protecting historic buildings. It was his Twitter account, however, now deleted, that really rubbed salt in the wound.

In one post, as part of the hashtag game #badlyexplainyourjob, Mr Martyn said that he was “destroying dreams and standing in the way of progress by saying old stuff is nice”. In another he posed with a stuffed lion on his head and the words: “Conservation sheriff of the wild west”. But the post that seems to have most enraged local architects was a picture that showed him brandishing a unicorn glove puppet, captioned: “Mr Grunwald considers your listed building application invalid.”

George Ferguson, a former mayor of Bristol and former president of the Royal Institute of British Architects, led the protests and has since made an official complaint to the council. As well as taking exception to the Twitter posts, he accused Mr Martyn, who joined the local authority a month after Mr Ferguson ceased to be mayor, of “throwing his weight around” and demonstrating a lack of expertise.

“He’s clearly a prat on social media, and it’s all a bit childish,” Mr Ferguson said. “He’s been very arrogant on site to more experienced architects and unpredictable: he’s asked for the preservation of things — like flagstones in a pub that was being redeveloped — that he didn’t realise were new. South of the river, in Bedminster, an area of two to three storeys, he advised a developer to increase the height of their building from six storeys to nine, so it’ll stick out like a sore thumb.”

Robert O’Leary, of O’Leary Goss Architects, said that he had advised some clients not to pursue further refurbishment projects because of the difficulties of obtaining planning permission and that Mr Martyn, also a qualified architect, had given developers “the run-around”.

“He described one unlisted building as being of extreme national importance,” he said. “But that’s ridiculous — how can it be of extreme national importance if it’s not listed? There’s a real concern that Bristol is being held back by the weight of heritage, and can’t produce new, exciting buildings.”

The council pointed out that 90 per cent of applications related to listed buildings last year were approved and that most new schemes in Bristol were in conservation areas or near to a listed building; there are 4,000 in the city compared with about 1,000 for most large urban areas outside London.

“I talked to him and the posts were taken down,” Vicky Smith, Mr Martyn’s boss at Bristol city council, said. “But heritage decisions are not just based on an individual’s views and we’ve had lots of compliments about how David works with applicants.”

Mr Martyn said: “I’m not sure if I’ll be putting my Twitter account up again.” And what about Mr Grunwald? “He’s in safekeeping. But I don’t think he’ll be making any more appearances.”

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