What is the purpose of numbers on some UK street name signs?

As a frequent traveller around the UK I have developed a somewhat unhealthy obsession with street signs and their small but significant differences.

Can someone explain what the purpose of the small numbers sometimes seen on street name signs are? I have concluded that it is not to do with Post Codes or house numbers. My only thoughts are that it is a numbered entrance to a street for those unfamiliar with the area, street design or layout. If that is the case then why aren't those unfamiliar with the area made known about this numbered system?

See example below. What is the purpose of the Number 5?

Edit. More examples below.

enter image description here

uk driving factoids identify-this

Pictures about "What is the purpose of numbers on some UK street name signs?"

What is the purpose of numbers on some UK street name signs? - Woman in White Hoodie

What is the purpose of numbers on some UK street name signs? - Letters And Numbers Engraved In Stone

What is the purpose of numbers on some UK street name signs? - Signboard with inscription on wooden board

What do the numbers on street names mean?

However, in most cases, the street number is the number describing where a building is located on a street. It can also be listed as \u201chouse number\u201d, but it goes without saying that businesses will not use this term when giving their address.

What are the numbers on street signs?

Reference markers are small green signs with three rows of numbers provide a unique locator for every state road. The top number is the route number. The second line identifies the DOT region, the county, and the sequence of the county along the route.

What is the purpose of street name sign?

A street name sign is a type of traffic sign used to identify named roads, generally those that do not qualify as expressways or highways.

How are road names decided UK?

City, borough and district councils allocate postal numbers to houses and buildings in their area. They also name new roads and streets. The council involves the land developer in the street naming process. They invite suggestions and possible alternative names from the developer.

Understanding Road Markings | Learn to drive: Highway Code

Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.

Images: Pixabay, 任力, MART PRODUCTION, Ashford Marx