A space must separate the two parts<\/li>\n<\/ul>\nKey idea:<\/strong>
\nIf the structure is wrong, it is immediately invalid.<\/p>\n
\n<\/span>2. Check the Outward Code Pattern<\/span><\/h2>\nThe outward code can take forms like:<\/p>\n
\n- A9<\/li>\n
- A9A<\/li>\n
- AA9<\/li>\n
- AA9A<\/li>\n
- A99<\/li>\n
- AA99<\/li>\n<\/ul>\n
Example:<\/p>\n
\n- M1 \u2714 valid<\/li>\n
- M123 \u2716 invalid pattern<\/li>\n<\/ul>\n
Key idea:<\/strong>
\nThe first half must match allowed UK patterns.<\/p>\n
\n<\/span>3. Check the Inward Code Format<\/span><\/h2>\nThe inward code must always be:<\/p>\n
\n- 1 number + 2 letters<\/strong><\/li>\n<\/ul>\n
Example:<\/p>\n
\n- 1AA \u2714<\/li>\n
- 12A \u2716<\/li>\n
- AAA \u2716<\/li>\n<\/ul>\n
Key idea:<\/strong>
\nThis part is strictly fixed in format.<\/p>\n
\n<\/span>4. Check Against Known Area Letters<\/span><\/h2>\nValid area codes include:<\/p>\n
\n- M (Manchester)<\/li>\n
- B (Birmingham)<\/li>\n
- SW (South West London)<\/li>\n
- E, N, W, SE, etc. (London zones)<\/li>\n<\/ul>\n
Example:<\/p>\n