The TV ad, created by Abbot Mead Vickers BBDO, features viewers' reactions to the Games.
The ad breaks tonight (6 August) during 'Coronation Street' on ITV1. It features a large crowd celebrating the games in Hyde Park, where the telecoms company has been hosting live screenings and events during the course of the Games.
The voiceover states: "Every high, every low, shared by millions, BT's fibre optic network, at the heart of the Olympic and Paralympic Games."
It closes with BT’s strapline for the games, "BT: Bringing us all together."
The ad will run until mid-September and is supported by an outdoor campaign running on busses, BT phone kiosks, 750 London taxis and on JCDecaux's Transvision screens in major national train stations.
Dave Buchanan and Mike Hannet were the creative directors on the campaign. The copywriter was Martin Lorriane and it produced by Rattling Stick.
Suzi Williams, director group marketing and brand at BT, said: "As the official communications services partner our new advert is a great way to showcase how BT is connecting people to some truly memorable moments.
"We are immensely proud to be bringing so many people together to share in the magic of London 2012."
"Tim Berners-Lee tweeted live from the Opening Ceremony to signal the most connected Games ever.
"Athletes in the Village are tweeting, over 20,000 media on the Park are filing their reports, sending photographs and broadcasting to the world and there are 25 million visits daily to the London 2012 website. BT's fibre optic network is at the heart of that."
In the lead-up to the Olympics BT ran a TV campaign using its avatar characters, used in its print ads, doing synchronised swimming.Follow @shearmans