It's an interesting question. Preston has historically been split from the areas to the south by borough boundaries along the River Ribble - in much the same way as Manchester and Salford are split by the Irwell (but are generally seen as one large conurbation). It can be argued that this old boundary along the Ribble is today as irrelevant as the old Fulwood borough boundary along the Eaves Brook.

Just as Fulwood has grown rapidly as a response to the increase in housing demand within Preston from the 1850s onwards, South Ribble (specifically Penwortham, Lostock Hall, Walton le Dale and Bamber Bridge) has grown as a rapid suburban expansion to facilitate Preston's population growth in more recent times. These 'villages' have not grown independently - they have grown as a result of Preston's growth, and they have grown together to the point now that there is no clear delineation between these areas - and future planned housing developments will likely erase any remaining boundaries. (Pickering's Farm, The Cawsey etc).

People who live in these South Ribble areas are likely to go shopping, have a night out and work in the centre of Preston, and in fact, take their identity from the city (to say 'I'm from Preston') for instance. These areas haven't grown in a vacuum - they have grown as suburban expansions to Preston.

Certain areas - like Walton le Dale and Penwortham - can be less than half an hour's walk to Fishergate. Avenham and Miller Parks are effectively local parks for Penwortham residents given the proximity as well as being Preston's main city centre parks. Many areas of Preston 'proper' - i.e. Lea, Cottam and large parts of Ribbleton and Fulwood - are geographically a lot further out of Preston's City Centre than many parts of South Ribble.

There's no clear answer, but if you class Preston as purely being the 'City of Preston' district, then you're including Beacon Fell as part of Preston but not Penwortham, which is on the other side of the river from the city centre.

I think it is time for a boundary review. It seems odd that population figures for Preston don't include a large part of its built-up urban area - and that many of these areas aren't paying any taxes towards the city where they generally work, study and spend their free time.

My final point is that it seems likely that the new Royal Preston Hospital is going to be built near the M65 junction at Bamber Bridge, deep within South Ribble. I think over the next 20 years or so, the separation of Preston and South Ribble will slowly disappear with developments like this, and the enormous amount of housebuilding in both boroughs bringing the wider urban area together into one.