Allen & Overy and Simpson Thacher & Bartlett are advising on the sale of U.K. waste company Pennon Group’s recycling business to one of private equity giant KKR’s newly-foundde company.

Pennon Group is selling its subsidiary Viridor, a recycling and waste management company, to Planets UK Bidco, a new company formed by private equity house KKR. The transaction is worth £4.2 billion, according to Pennon Group’s statement.