From King’s Cross St Pancras, take the Piccadilly line directly; if crowded

https://www.scribd.com/document/1074929924/National-Rail-to-Heathrow-Routes-Transfers-and-Tickets-Explained-232993

From King’s Cross St Pancras, take the Piccadilly line directly; if crowded, consider one stop on the Circle/Hammersmith line to an easier interchange at Paddington.