The Heathrow Express from Paddington reaches the airport in about 15 mins

https://www.scribd.com/document/1074894734/Heathrow-Drop-Off-Charges-and-Pick-Up-Locations-Avoid-Fines-and-Hassles-212266

The Heathrow Express from Paddington reaches the airport in approximately 15 minutes. It’s the quickest rail preference, though pricier than the Tube.