It turned out that they were filming some scenes from a film titled "Hippy Hippy Shake", which is set in London in the early 1960s. I'm not sure whether they were using Portobello Road to stand in for a generic street in early-60s London (which would presumably have been quite expensive), or whether they were actually filming a scene set in Portobello Road, and in which case, whether the shops they had reconstructed had actually once existed there. (Then again, there was someone carrying a Blenheim Crescent street sign, which presumably had been temporarily taken down, so perhaps they were actually reconstructing the intersection two blocks down circa 1962 or something?)