The number of UK-based browsers has tripled, up from 1.3 million who read the site in August 2011, the first full month since the launch of the UK operation.
"Unique users have increased three times since launch, average daily users have increased 11 times over and the average time per visit has risen by 79 per cent," Carla Buzasi, editor-in-chief of Huffington Post UK told Journalism.co.uk.
The UK site is also averaging 100,000 user comments a month and has 11 times the number of bloggers it had at launch, growing from a community of 300 to 3,300 bloggers, Buzasi said.
The team of staffers has grown too, from eight at launch and there will be 25 by the beginning of next month.
"I'm really, really pleased with how the first year of the site has gone," she added. "It's been pretty full on, everyone has worked incredibly hard but I don't think even we could have predicted the splash that the site made in the British media scene."
Remembering the riots
Asked for her memorable moments of year one, Buzasi said the England riots "were a high point in terms of the coverage".
"We had people all over London reporting back to us and it showed how Huffington Post can do things differently. We instantly had people blogging for us who were living in these areas and who were seeing it first hand. As well as having our journalists there we were able to get real people on the streets who were living and breathing it and sharing their opinions on it.
"We then had Newsnight and radio stations phoning us up and the people they wanted to talk to were the bloggers rather than the journalists as they had a different take on the events."
Mobilising with mobiles
Another memorable day for newsroom-based members of team was in April when there offices were evacuated during a siege on Tottenham Court Road in London.
The site's executive editor, Stephen Hull, turned to reporting from his iPhone and clocked up 5,000 new Twitter followers as he shared updates and videos that when viral.
"It shows how we can mobilise really quickly and that the site can be run via people's phones.
"It also shows how new media can take a story and really run with it and do it in a way that gets the information out really fast."
New sections, new editions
Since launch on 6 July 2011 the Huffington Post UK has added several news sections. It added sport in March, technology, universities and education, and at the end of last year launched culture and celebrity sections, both on the same day.
"This showcases the breadth of content that Huffington Post UK now covers," Buzasi said. "As well as having the high-brow, intellectual content, we have also got the fun guilty pleasures on there as well."
Within the past year the Huffington Post has launched other international sites, Le Huffington Post in France and El Huffington Post in Spain. Both came to life through partnerships with established news providers, El Mundo in France and El Pais in Spain.
Asked why there was no partnership deal done In the UK, the first expansion beyond the US, Buzasi said it was because AOL was already established here whereas the company "did not have a big presence" in France or Spain.
"We had offices, there were people in place in the UK, and that enabled us to launch really quickly."
The Huffington Post UK both reaches out to new bloggers and "receives hundreds of emails" from people interested in writing for the site.
"It's probably about 50:50 in terms of people coming to us and us approaching people."
It has also gathered offers and interest from high profile bloggers. David Cameron, Nick Clegg and Ed Miliband have written for the site and Prince Charles's team offered videos being broadcast at the Rio Earth Summit to run as blogs.
Huffington Post UK has found success on social media. It has done so by recognising different platforms work for different types of content. For example, Pinterest works for the title's fashion content, whereas sport gathers traction from other platforms.
Social and search bring in roughly equal numbers of readers overall, according to Buzasi, with some sections, such as comedy, doing particularly well on social.
Looking back on the first year Buzasi said: "We are over the moon and looking forward to making things bigger and better in year two."