Davies, who will take up the UK job in mid February, replaces John Shaw, who will return to Portland to work on the Coca-Cola account after a two-year stint in London.
In 1999 Davies, a British native, moved to W&K Portland to work as the senior planner on Microsoft before becoming planning director for the whole agency. Before this, he was running Leo Burnett's UK interactive division.
Davies said: "I wanted to go back to what I have enjoyed most about advertising. Making brilliant ads and working with a group or really good people I know very well, within the W&K ethos. Plus, I missed Match of the Day!"
Amy Lawson, managing director of W&K London, added: "Russell has a terrific sense of humour and a great understanding of what is going on in contemporary culture. I am thrilled to have him and he will build on the considerable effort made by John Shaw in the past couple of years."
"It's great to have someone in the family already. He'll bring an international perspective and knows how to access our network. He also has the West coast, new economy experience and this will be an asset."
Davies worked on the Alta Vista launch in the US 18 months ago and also on the launch of Microsoft Office 95 and Windows 2000.
Lawson said she hopes Davies' international experience will help the London office chase international business. She said: "I want us to ramp up our pan-European work as well as not just this market."