I need to go and come back a lot between London and Sheffield for the next year. What is the fastest way to travel between these two. I looked into trains time-tables and they are all 2 hours+.
WikiTravel has a quite extensive guide on Sheffield. Looking for travel options,
Google Maps suggests that the distance is coverable by car in 3 hours and is about 160 miles, which seems a reasonable estimate.
London St. Pancras, once per hour, operated by East Midlands Trains.
Looking at their website tells me that it would take at least 2 hours and 1 minute to get there, which also seems quite reasonable according to the distance.
Even though Sheffield is a prominent city, the closest airport from the city is Doncaster-Sheffield Robin Hood Airport(DSA) which is 35 minutes by car.
This would make it infeasible to travel from London because the distance is simply too short and the train trip would be faster anyway (think boarding into flights and landing, luggage etc.)
Thankfully, airlines seem to agree with that and yes, there are no direct flights from London to Sheffield.
So, your best bet is to take the train and enjoy the happy ride for 2 hours and 1 minute.
There are no direct flights from Doncaster-Sheffield Airport (DSA) to any London airport.
Sheffield-London uses the Midland Main Line, which is not a particularly fast main railway line. The fastest services take two hours and one minute.
Depending on exactly whereabouts in Sheffield you are leaving from, you might be able to use trains from Doncaster, which use the (faster) East Coast Main Line in about 1 hour and 42 minutes.
Note that the UK Government agrees with you that Sheffield-London takes too long, and has started a programme to upgrade the Midland Main Line by 2020, which will reduce timings by about 15 minutes, and by the proposed construction of HS2, which would see trains taking about an hour from London to Sheffield after 2030.