as per the following specifications:

FORMAT EXAMPLE AN NAA M1 1AA ANN NAA M60 1NW AAN NAA CR2 6XH AANN NAA DN55 1PT ANA NAA W1A 1HQ AANA NAA EC1A 1BB

• The letters Q, V and X are not used in the first position
• The letters I,J and Z are not used in the second position.
• The only letters to appear in the third position are A, B, C, D, E, F, G, H, J, K, S, T, U and W.
• The second half of the postcode is always consistent numeric, alpha, alpha format and the letters C, I, K, M, O and V are never used.