The list of agencies visited included Grayling, Fleishman-Hillard, Lexington Communications, Brunswick and Burson-Marsteller.
'It's more theatrical than giving a lecture,' said SpinWatch's David Miller, explaining it was able to run the academics, students and journalists through several exercises to gain an insight into the London PR scene.
Moments after passing H&K's conspicuously branded building, the walkers failed the challenge of trying to find out which agency was housed in one Shaftesbury Avenue building (lobbying firm Foresight Communications).
Another experiment had walkers posing as property developers looking for a quote for vacant office space that Miller claims is rented by Interpublic Group PR firms. He says conservative estimates gleaned from the building's co-habitants were £350,000 a month - evidence Miller says, of what he sees as the industry's excessive ways.
More walks are planned.