London Mayor Boris Johnson was caught by surprise when a PR stunt at a Barnet redevelopment project he helped to fund was hi-jacked by an angry campaigner.

During a visit to the Dollis Valley Greenwalk in Finchley this morning, the Conservative politician was “marched around” and “shown everything that is wrong” with the landscaping work.

Chairman of the conservation group Friends of Windsor Open Space (FOWOS) Dennis Pepper was coincidentally showing a Times Series photographer “unfinished” and “hazardous” parts of the completed project when the mayor unexpectedly arrived on his campaign trail.

What was supposed to be a positive PR stunt for the journalist turned politician soon turned into a swift grilling by Mr Pepper who led the mayor around areas of the park his aides did not want him to see.

A total of £400,000 was handed to Barnet Council from the mayor’s office to help complete the regeneration of the concourse, which included new walkways and cycle lanes.

Since its completion earlier this year though, FOWOS members have complained that areas of the open space have been left unfinished and looking untidy.

An entourage that included Finchley Church End councillors Daniel Thomas and Eva Greenspan and Barnet Council leader Richard Cornelius were left “looking uncomfortable” as Mr Pepper listed the project’s faults in front of the visiting mayor.

Windsor Drive resident Mr Pepper said: “I more or less marched him off and I got a chance to explain to him why the worst bits had not been done.

“I didn’t expect to see him at all – no-one told me he was coming to visit. They wouldn’t want me there to spoil the party anyway.

“It was pure coincidence and I’m sure all of our local delegates were very annoyed but he did give me the chance to speak to him directly.

“I went over to him and he offered me a leaflet in a kind of ‘vote for me’ gesture and I just told him I had something else to talk to him about.

“His aides were showing him one piece of the path that looked very nice but round the corner it hasn’t been improved at all so I took him round there.”

The former Shadow Minister for Higher Education chatted with Mr Pepper as the group was led around the park and reportedly appeared unfazed by the change in schedule.

Mr Pepper added: “We’re all for the project but we want to see it done properly. It was surreal and totally unexpected and whether it will do any good we will have to wait and see but I’m glad I was able to show him something he has funded that has been done badly.”