History programme on Channel 4 schools (I think?)

Does anyone remember a history programme that aired on Channel 4 schools? It was about this guy going to different time periods (e.g. Greek, Victorian etc) but he can see them but they can’t see him. I watched it in school during the Channel 4 schools block (I think but not 100% sure). Can you tell me the name of the programme, please?

Don't think it's Living Proof, a game show that went through different periods of history each week. Actor was a comedian by trade. What year do you think you saw it?

It was in the mid 2000’s.