The deal comes less than a year since fellow UK BPO innovator Astron was snapped up in a $1bn deal by RR Donnelley, and almost a year to the day since FedEx acquired quickprint chain Kinkos.

"What you are seeing is an effort by fulfilment companies to jump in so they can do the physical delivery, and eventually all forms of document delivery," said Brian Miller, associate director of document outsourcing at research firm InfoTrends. "This whole market was pioneered in the UK and Williams Lea and Astron have been tremendously successful."

3i divested its 38% stakeholding for 110m, with some members of the Williams family agreeing to sell part of their 30% stake in a deal that values the firm at 450m.

DPWN has an option to purchase the remaining stake in Williams Lea in the next three years.

"We have structured a deal that allows us to grow the business and invest further, said Williams Lea chief executive Tim Griffiths (pictured).

Griffiths said that following the decision last year by 3i to divest its stakeholding, Williams Lea appointed investment bank UBS to review its options.

Williams Lea would strengthen its presence in global mail market said DPWN, which owns DHL Global Mail.

The existing management team, led by Griffiths, will remain as will the Williams Lea name.