Robert Walton has written to the public prosecutor in Spain, his sister Rachel Walton said.

BBC: Garry Walton drowning: Family seeks appeal

When in 1676 Robert Cotton, the younger man whom Walton treated as an adopted son, joined his own work to Walton's, creating "Walton and Cotton's Angler, " he brought to the partnership the use of angling with dry flies.

WSJ: It Has Hooked Generations of Fishermen | Izaak Walton | The Compleat Angler | By H. George Fletcher

"I went after Robert Thompson, arrested him and took him to Walton Lane police station to interview him, " he told BBC Radio Cymru.

BBC: James Bulger