Only one unit was built , no. 89001 , which was officially named Avocet by the then Prime Minister Margaret Thatcher on January 16 1989 at Sandy , Bedfordshire - the home of the Royal Society for the Protection of Birds ( whose logo is an avocet ) . Only one unit was built , no. 89001 , which was officially named Avocet by the then Prime Minister Margaret Thatcher on 16 January 1989 at Sandy , Bedfordshire - the home of the Royal Society for the Protection of Birds ( whose logo is an Avocet ) .