Here’s a breakdown of the factual shows mentioned in the text:
Genghis Khan series for Nat Geo: This is a factual series about Genghis Khan commissioned by National Geographic.
Country house show that has been pre-bought by Channel 4: This is a factual show focused on country houses that has already secured a broadcast deal with Channel 4 before its production is complete.
what Really Happened: American Independence: this is a documentary series being made for the 250th anniversary of the Declaration of Independence in 1776.
A follow-up from Dash’s earlier show Frontier: This indicates another factual series that is a continuation or related project to Dash’s previous show called frontier.