Here is where a 20mph road (St Ronan's Road), crosses a through road, Albert Road. Hence signs saying you can go up to 30 to drive across this road, then back down to 20
It also partitions the two 20 mph zones: there's now a more dangerous road in the middle.
Elsewhere, here is some signage announcing you are in a 20 section. Because pavement's don't have enough clutter. Maybe if you could embed miniature 3G mobile phone base stations in the signs, a mobile telco will fund for the right to put them up everywhere.
This road doesn't have any signs. Its a dead end, cars on pavements both sides? Is a 20 mph or a 30 mph road then?
The answer, although not obvious is 30 mph.
St Helen's Close is off St Helen's Road, and that is an A-road, hence 30 mph. This side road has no speed limit signs, so its speed is that of the sole entrypoint: 30mph.
This dead end, then with is pavements occupied by cars, is not a street for small children to play football in the road in. Montpelier has better community streets than this.
[Incidentally, email has been received asking why spend xmas in Portsmouth? The reason for the trip was family related, and that small piece of parental responsibility that regularly complains about the quality of the ride while being towed behind my bike says it was the best part of his xmas holiday. Which really is sad, and is the kind of statement which probably brings Bristol Social Services to your door if said in hearing range of a school teacher]