Calvert, UK. 27 July, 2020. A large tree at Calvert Jubilee Nature Reserve. On 22nd July, the Berks, Bucks and Oxon Wildlife Trust (BBOWT) reported that it had been informed of HS2’s intention to take possession of part of Calvert Jubilee nature reserve, which is home to bittern, breeding tern and some of the UK’s rarest butterflies, on 28th July to undertake unspecified clearance works in connection with the high-speed rail link.