The tour starts at Farringdon where the first trains ran underground in 1863 and ends with a look to the future at Westminster station.
Rather than ruin the tour by telling you everything that's on it, some of the things you'll experience are discovering which line may have been called the Viking Line, seeing where a "ghost Tube station" is and learning about some of the interesting things encountered when the Victorians were digging tunnels by hand.
As someone who uses the Tube at lot and has been writing about it for years, I was pleased to see some new things to look out for. The tour would a good way for tourists to while away some hours & speak knowledgeably about the Tube when back home. Tube experts or those with a more geeky knowledge may want to get something a little more tailored for their "specialist" subject. But Insider London would be happy to do this.
Naturally, the tours don't run in the rush hour, as we all know how much we love to see groups of people standing around pointing at things on a commute! However, as long as there's a minimum of two people, you can get a tour to suit the day & time that's best for you. There are also discounts for 10 or more people.