Great Britain road numbering scheme

In Great Britain, roads are given a letter with 1-4 numbers after it. This is how they are named. The letter is the category of the road. There are two main types of categories: motorways (with the letter "M") and non-motorways. There are two types of non-motorways: A roads (with the letter "A") and B roads (with the letter "B"). A roads are more important than B roads. There are also a very small number of C roads.
This system only applies to the island of Great Britain. Northern Ireland and other islands have their own systems.
A roads.
Single-digit A roads.
In England and Wales, the six A roads with one number are most important roads coming out of London. Starting with the A1 which goes north, numbers go clockwise around London:
In Scotland, important roads from Edinburgh have A roads with one number: