I am travelling with my family for a holiday in England. I am looking at renting an apartment in Covent Garden. What would be the drive time to and from Heathrow airport?
If you're planning to rent a car and drive to Covent Garden, one word of advice: DON'T. London traffic and parking charges (not to mention the Congestion Charge) are mental and no Londoner in their right mind would drive into the centre, let alone a tourist.
If you're getting a black cab (taxi), bear in mind it could be quicker than a Google estimate, as London cabs can use dedicated bus lanes and the drivers have years of experience. The time it will take will vary hugely depending on the time of day. Anything from 30 minutes in the middle of the night to 1.5 hours (and up) in the morning rush hour.
If you're going to get the Underground, that goes direct to Covent Garden (the Picadilly line). This would probably be the quickest option and since the line starts at Heathrow, you're guaranteed seats.
Google maps gives an estimate of one hour to drive from Heathrow to Covent Garden.
However - I would not recommend doing so. Driving in London is best avoided even if you're a local, and parking near Covent Garden, if you can find any, will be very expensive.
I'd recommend taking the Underground - there is a direct train from Heathrow to Covent Garden on the Picadilly line, taking around 50 minutes.
I live not far from Covent Garden, although a little further out, still in the City of Westminster. I go to Heathrow a few times a month, usually by tube but sometimes in the car. In my experience it is about an hour's drive, mostly because of congestion in the centre, but at certain times of the day it may take much longer, so it can be hard to plan how much time you need.
I'll contradict the other answers here and say that driving in London is not that difficult compared to most European capitals, at least in my view. But I would recommend you take a taxi or an uber instead of hiring a car. Parking in Westminster for non-residents is not easy to obtain, there is a fee to enter the centre of town, and the roads are fairly confusing. At a minimum you should arrange parking in advance if you really think you need a car.
I would also echo the advice to take the Tube if it's easy for you, but I'll add a bit of balance and say if you do have a lot of luggage or elderly people or young kids in tow, central London public transport is very busy, it can get very hot and extremely crowded, people can be very unforgiving at rush hour of confused people with large bags, and you may find sitting in the back of an uber is much less stressful and more civilised. I usually pay about £40 for an uber each way. If you're not a fan of uber, it is cheaper and more comfortable to book a car in advance (a "minicab") rather than try to hail one at arrivals.