The move, which will see CPT effectively take over the London and Peterborough-based practice, is the latest in a line of recent big-name buyouts by the architectural arm of multidisciplinary behemoth Capita Symonds.
Only three months ago CPT snapped up the Birmingham branch of Church Lukas, having acquired Norman + Dawbarn last year.
The combined workforce of Ruddle Wilkinson, which employs 30 registered architects, and CPT, which boasts 172, will create the country's second largest practice.
Only the Building Design Partnership now has a larger UK-based staff.
Although the name of CPT's latest target was not officially known until today, the deal has not come as a surprise.
Just before Christmas, the mammoth practice announced it was eyeing up a series of architectural takeovers ( Capita plans architectural acquisitions).
Details of exactly how the acquisition will work remains unclear and the deal is not expected to be finalised until next week. Ruddle Wilkinson has previously focused on transport, education and commercial work.