Producers of the longrunning kids show have asked fans for help in tracking down the unnamed actor who played teacher Gordon Robinson in the programme's 1969 test pilot.

A post on the Sesame Street website, accompanied by footage of the mystery man, reads, ""We don't know who he is, and we'd like to figure it out. We've tried everything short of asking the internet, and come up empty. So we're asking you for help.""

Roscoe Orman, Matt Robinson and Hall Miller have all played Gordon over the years