Some paths have disappeared! Walking around the sites in Chiswick it’s clear that some of the allotment paths have disappeared under cultivation usually.
You should be able to walk around your allotment on a path about 2 feet wide – wide enough to wheel a barrow down. As you face your allotment from the main path the path on the right hand side of the plot is your responsibility. Even if you have two plots next to each other you should still maintain the dividing path – it won’t be your plot forever.
If paths have had shed, polytunnels or green houses erected on them or have been assumed into a plot the council can insist that these are removed and paths reinstated.
To misquote Robert Frost – “good paths make good neighbours”.