These business people aren't very business like I would say. Did a brenchmarking this summer between Manchester and London, and the train travel took around 1 hour 40 minutes less than with the plane. The trip north was from London Euston to Manchester Piccadilly with Virgin Trains in First - travel time 2 hours 8 minutes. The trip south again was from Manchester Piccadilly to Manchester Airport with Trans Pen in First, MAN-LHR with Little Red (to keep it in the family) and the Heatrow Express in First from Heathrow to Paddington. At Paddington the watch stopped at 3 hours 47 minutes. The trip was done with no checked in luggage - only an iPad to stay online and a small Canon to document the trip. If the trip had started at Gatwick the difference between the options would had been even larger. I haven't said a thing about the stress level difference (the safety check at MAN T3 was awful) and price tag difference, but I can tell you the train won it hands down on all accounts. Oh, I didn't mention Virgin Trains served a wonderful full English breaky free of charge.
2 hours 8 minutes is a reasonable time for Manchester-London city centre-city centre journey (makes one wonder if £50 billion to cut less than an hour off the journey time is a good use of public money). For this kind of journey clearly the train is the best option.
But don't forget the onward travel times to/from London-Euston. A final destination does
not have to be very far from the centre of London to add a couple of hours to the journey.
For those heading west of London, a Ringway-Heathrow flight can often be the most convenient option.
It's good to have the choice.