I confirm that Ordnance Survey does hold some of the information you have requested. Where the information is not held or exempt this is stated.
Taking each request in turn, I confirm the following:
1. A copy of the letter before claim you sent the AA to start the whole process
I confirm that Ordnance Survey does hold a copy of the requested information, please see the letter before action dated 8 October 1996 from Ordnance Survey to The Automobile Association (PDF).
We do not hold a copy of the Memorandum referred to in the attached letter.
Whilst we are able to release the attached letter, note that we have redacted the signature on the letter as it is exempt from disclosure under section 40(2) (Personal Information), of the FOIA as it constitutes personal data. Section 40(2) provides that personal data is exempt information if one of the conditions set out in section 40(3) is satisfied. In our view, disclosure of this information would breach the data protection principles contained in the General Data Protection Regulations (GDPR) and the Data Protection Act (DPA) 2018.
Section 40(2) is an absolute exemption and therefore not subject to the public interest test.
2. Details of the 'fingerprinting" process by which you detected that the AA had copied your maps
I confirm that Ordnance Survey does not hold the information you have requested.
Ordnance Survey detected that AA had copied our mapping by comparing the maps with our own mapping and identifying where unique cartographic styling, which distinguished Ordnance Survey mapping from other mapping had been used by the AA; this process was referred to in the litigation as “fingerprinting”.
Under the duty to provide information and assistance in accordance with section 16 of FOIA, you may find the following published articles useful:
Copying maps costs AA £20m | UK news | The Guardian. In particular, the following quote: Ordnance Survey’s “fingerprints” did not extend to putting misleading features in maps: “There are some publishers who put deliberate mistakes in their maps. We don’t do that - it would mislead our customers. For us, it’s more about the style we use.”
AA loses way in map dispute | marketinglaw (osborneclarke.com)