Wikipedia
Porterbrook is one of the three major rolling stock operating companies (ROSCO) in the United Kingdom (the other two being Angel Trains and Eversholt Rail Group). It owns around a third of passenger railway locomotives, multiple units and coaching stock running on Network Rail's system which it leases to various train operators.
Since 1996, Porterbrook has spent more than £1.5bn on new rolling stock in the UK and also leases to freight companies Freightliner, GB Railfreight and DB Schenker. It also expanded to hire locomotives and stock on the European Continent, however the European operations were sold to CBrail in 2004.
The company has been owned since October 2014 by an international consortium comprising Alberta Investment Management Corporation, Allianz Capital Partners, EDF Invest and Hastings Fund Management.