For a tech firm it's old - BT's origins lie way back in the mid-1800s, predating even Alexander Graham Bell's invention of the phone in 1878. For much of the 20th century it was part of the Post Office, but the modern BT story really began in November 1984 when it was privatised. Mrs Thatcher sold 51% on the London Stock Exchange, so we punters could reap the benefits of more choice, better service and lower prices. That's the theory anyway.
BT's fundamental challenge has been how to compensate for the fact that people use their landlines less and less, and mobiles, tablets and PCs more and more. Getting into the mobile biz looked like a no-brainer, but a £20bn post-dotcom crash debt crisis forced the sale of its first attempt - remember Cellnet? - back in 2002. Oops.
Its next big wheeze fared better, upgrading much of its ageing phone network to fibre optics, the backbone of the UK's high-speed broadband infrastructure. Whichever ISP you have, if your internet comes down the phone line, it is BT's Openreach subsidiary that laid the cables, maintains the system and reaps the benefit of wholesale charges for doing so.
Sadly just as things were looking up, ill-conceived consulting arm BT Global Services tanked. Shares hit an all-time low of 97p thanks to a whopping £2bn of charges in 2008-2009. That's a lot of calls to your Auntie Mabel, even at peak rate. Cue a round of drastic cost-cutting, thanks to then CEO Ian (now Lord) Livingston, who put his accountant's training to good use. Free cash flow has hit £2.8bn, up from only £770m in 2008.
Who's the boss?
Ex-P&G marketer Gavin Patterson took over from Livingston in Sept 2013. Not only is he the sharpest-looking boss of BT in living memory, he is also one of its most radical, investing £20bn in a huge content drive to see off rivals Sky and Virgin. Over £1bn has gone on football rights, as well as the UK rights to US drama channel AMC, maker of the Mad Men series.
But it's BT's re-entry into the mobile business that will make or break his reputation. Subject to regulatory approval, the £12.5bn deal to acquire EE is on and will give BT the distribution network to match its content ambitions. If all goes according to plan, then come 2025 or thereabouts, BT's venerable landline service will finally be switched off.
Customer service. The City may have fallen back in love with BT's story - shares are over 440p, a 15-year high - but unhappy punters definitely have not. BT remains one of the UK's most complained about companies, with long hold times and clueless call-centre staff the most common gripes. Isn't competition wonderful?
Pre-tax profit: £3.17bn