Protesting workers staged a sit-in and chained the doors of the Gratte Brothers office.

And fellow contractors are expecting more of the same today as the long running protests against plans by major firms to pull out of the JIB pay deal come to a head.

Rank-and-file sparks will stage demonstrations across the country as the Unite union prepares to re-ballot members at Balfour Beatty Engineering Services over possible strike action.

Protests are planned outside SSI steel works Redcar in Hartlepool; Cardiff Hospital, Wales, St Catherine’s Hospital in Birkenhead, London’s Thameslink site at Blackfriars and Balfour Beatty’s head office in Glasgow, Scotland.

But contractors fear the sparks could intensify the action following the Gratte Brothers invasion.

One told the Enquirer: “We saw what happened last month when they stormed into the reception of Grattes.

“I can see the same sort of thing happening again so we’ll have to be on our guard against people trying to get on our sites or into our offices.”

A website run by the rank-and-file protesters said: “Lets shut down Balfour Beatty – not just in the morning but 24 hour pickets from 7th December onwards.”