Do you or he not know that double-yellow lines mean "No parking 24x7" ? There are two exemptions to this, (1) loading/unloading and (2) boarding/alighting passengers. From your narrative, neither of these exemptions applies, as " to get a dessert", doesn't sound like loading, unless it was of a nature that required him to park close to the collection point.
He could have been walloped for parking off the carriageway, which has been an offence in London since the 70s, and needs no signs or lines.
