(ShareCast News) - Engineering firm WS Atkins has agreed to sell its minority investment in the M25 motorway to a consortium of institutional investors for £66.3m.The FTSE 250 company will sell its private finance initiative in the motorway to Edge Orbital Holdings, which is being advised by broker Macquarie, subject to third party consents and is expected to be completed by the end of 2016.At 30 September the company held a £19.7m interest bearing loan notes in Connect Plus (M25) Intermediate, which it holds a 10% stake in along with a consortium including Balfour Beatty, Skanska and Egis Road Operation UK. The loan notes mature in 2039 with an interest rate of 12% per annum.