London has an enormous orbital motorway, the M25. If you imagine a clock, the M11 (Cambridge to London) joins at about 1 o'clock (about J24 IIRC). Heathrow is at about 9 o'clock (J15).

The fastest way from where the M11 joins the M25 to Heathrow (London's biggest airport) is to go anti-clockwise around the M25. Depending on the time of day, this should take (OTTOMH) about 30-45 minutes.

An alternative route would be to drive all the way in to the centre of London and back out again. This would mean you were liable to pay London's Congestion Charge. This route would take you about 90 minutes, be hell to drive and cost you money.

If Wayfinder are now suggesting routes through the centre of London, the routing algorithm is now seriously FUBAR.