Probably not the longest @Geordiebill as I know of a few who were with Cellnet and still here now, but it's certainly a long time
I doubt they would be able to tell you to be honest.
The oldest customer on the books is probably someone who has been with Telecom Securicor Cellular Radio Ltd / Cellnet / BT Cellnet since 1985 and will be an enterprise customer..
o2 has been around since 1985 in various guises... So if you have one of the original 04xx prefixes then you will be one of the oldest customers from the days of TACs. I think the original Prefix was 0401
Telecom Securicor Cellular Radio Ltd. became Cellnet became BTCellnet with the Genie Sub brand, which became o2 then sold to Telefonica.
edited as missed out BT
I miss Genie, was innovative
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