His coverage of East Timor's struggle for independence is listed in Unesco's Memory of the World register as a "turning point" in the birth of a new nation.

[3] He was the third of the four sons of Michael Alfred Wenner (1921–2020), a British author, company director, former diplomat who served as Ambassador to El Salvador (from 1967 to 1971),[7] and Gunnilla Ståhle (1931–1986), who was Swedish.

[10] On 14 September 1978, Wenner joined the British children's television programme Blue Peter, replacing John Noakes, who had left three months earlier.

However, he left on 23 June 1980 (on the same day as his co-presenter Tina Heath), after the production team decided not to renew his contract as he was "deeply unpopular with the viewers.

"[3][11][6] Wenner returned to acting, taking a part in the 1984 Doctor Who adventure The Awakening, although in the final cut, his role was reduced to that of a non-speaking character.

As soldiers advanced, in a well-organised operation against a huge crowd of East Timorese engaged in peaceful protest, he filmed inside the cemetery among the dead and the dying.

[16] In 2013, Wenner's audio visual material on East Timor's struggle for independence has been listed in UNESCO's Memory of the World Register as "On the birth of a nation: turning points".

He travelled there with cameraman, filmmaker and author Peter Vronsky in 1992 to report on the break-away republic and nuclear weapons materials smuggling for the Canadian produced television special The Hunt for Red Mercury.