Nothing has been lost since William Powell Frith painted his Derby Day panorama in 1858: today, instead of the carriages and corseted courtesans, the acrobats and pickpockets, he could cram his canvas with scarlet-lipped ladies in shades posing for selfies; with men in impeccable morning dress coping no better with greasy hamburgers than Ed Miliband did with his bacon sandwich; and with strolling musicians, from a moustached one-man band to the smartly co-ordinated Dukebox Singers, a sextet of ladies bravely striking up their acapella harmonies against the racing hubbub.