The 2012 Guardian Mobile Business Summit has just kicked off in London. And as you might expect, the first talk came from our host, as Guardian Core group product manager Anthony Sullivan took to the stage to talk about how the newspaper is adopting responsive design.

The Guardian is rebuilding all of its web services over the next 18 months, with mobile as its design starting point. The site is currently in beta, but will apparently go live next week.

Sullivan also spoke about why its time to move over to responsive design. Mobile traffic overall is growing – no surprise there – but the number of different devices has also exploded, with 1,857 different handset models being used to access the Guardian site last week.

Mobile neared 30 per cent of the total traffic during Q3, 2012, with an extra 10 per cent coming from tablets, and the two together already outnumber desktop visits at certain times of the day – notably 5-7am on weekdays, and around 3pm on Saturdays, once the Premier League football programme has kicked off.