Heathrow to Gatwick

Will you have checked luggage? Is this on one ticket? How are you travelling between airports? If everything runs like clockwork, it should be enough.

I would take the Elizabeth Line to Farringdon and then get on the Thameslink service to Gatwick.

You will need an ETA.

As Camborne said, since the Elizabeth Line opened it is much easier to get from Heathrow to Gatwick by train with one change at Farringdon. Alternatively, you still have the option of a direct bus between the airports.

Either way, though, five hours is pushing it given the stories I've heard about delays at Heathrow immigration for intercontinental travellers, the possibility of traffic delays or rail interruptions, and the need to arrive at Gatwick with time to spare.

Is this all on one ticket or are you self connecting? If on one and there are problems not caused by you the airline is required to get you to your destination. If self connecting it is on you.

There is a nonstop coach between the airports which is scheduled for 90 or 60 minutes.

If your Denver flight arrives on time and you have luggage and immigration done in 60 to 90 minutes, then that's about 3 hours from landing to arriving at Gatwick, leaving you 2 hours, pretty much the minimum check in time for the Faro flight.

If your flight is late, there are a lot of flights arriving with queues at immigration or waiting for luggage or you have to wait for the coach, or there is more road traffic than normal on the M25 or M23, I would say you might have an issue.

This is one ticket. We will have one checked bag each.

Have you already purchased the ticket? If so, can you change it to eliminate the airport change?

I see several Denver to Faro flight itineraries that change at LHR.

Do check this out, but I am reasonably sure you will have to retrieve your checked bags at LHR and take them with you. The airline does not shuttle checked bags between airports.

I would never have done this. What if your transatlantic flight is late? What if it takes you 30 to 45 minutes just to exit the aircraft? What if it takes 2 to 3 hours to go through immigration depending upon when you fly? What if it takes another hour to pick up that one checked bag? What will you do if it’s lost? The airline is not going to deliver it to Faro.

You have to arrive at Gatwick 2 hours early. I hope you are a gambler. This is not good.

BA considers this a legal connection, so it is possible to make it although this won’t be pleasant. If you have checked luggage, you need to pick it up at LHR. If you miss the connection because your inbound flight is delayed, BA is obligated to get you to Faro but it could end up being on a different day.

I would check for later flights to Faro that same day from both Gatwick and Heathrow. If your flight from Denver is significantly delayed, be prepared to talk to a BA agent to get you rebooked. If you arrive late to Heathrow and it is evident that you cannot possibly make your Gatwick flight, I’d go straight to a BA Agent for rebooking.

BA has a guide on their website:
https://www.britishairways.com/content/information/airport-information/flight-connections