Half a day in London

You're within walking distance of the Wellcome Collection, Foundling Museum and the British Museum; an organised walking tour of Bloomsbury would be interesting, weather permitting.

How about a tour of The Royal Albert Hall followed by lunch or tea there ?

There's the Charles Dickens Museum or closer is the British Library , but I second the British Museum lots to see there.

I second the Wellcome Collection - there is also the British Library - both are free as well. St Pancras Station - a real architectural experience.

perhaps hop on the tube, you will be just a few stops away from Covent Garden, always good to have wander round

What are the logistics with your luggage and getting to the airport?

The area behind Kings Cross has recently undergone quite a transformation, Granary Square, and can be an interesting stroll if the weather is good.
There's plenty to see and do in Bloomsbury - the British Museum is spectacular and there are lots of small places like the Charles Dickens museum in his London home. There are lots of interesting old bookshops to browse around. There's an app for your phone which maps all the Blue Plaques in London - you could stroll and look at where the good & great have lived.
If you fancy something more lively, Camden Market is around 15-20 minutes walk north but it does get very, very busy. You can walk along the Regents towpath to get there, which is a super walk.

Wellcome collection gets the thumbs up and it has a great cafe. Walk in The park Kensington Gardens/ Hyde Park if it’s good weather and will give you a breath of air before your flight. Go to see the Albert memorial/ Peter Pan fountains/ Diana playground/ boating lake with pelicans. The Saachi Gallery is free and has interesting exhibitions and is near some good shops/ cafes/ little parks etc.

The Britih Museum currently has an exhibition on the Scythians, warriors of Ancient Siberia It is bling fantastic

Here is a link to the Guardian review.
www.theguardian.com/artanddesign/2017/sep/17/scythians-warriors-of-ancient-siberia-british-museum-review

You need to book tickets in advance.

Re the Scythians Exhibition, it is half price for over 60s on Mondays after 12 noon. Good saving! (Take proof of age)

When I was there in August, on a weekday, I anticipate the queue to get in the British Museum would take up the whole 4 hours nicely.

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Depends on the sort of things that you enjoy?
If dry weather, I would be prefer to be outside, but you may enjoy browsing some good stores? Then an early meal or tea and cake and people watching?

I was with my GD (18) and we had tea and hot chocolate in Selfridge's. I got hot milk for the tea and it cost £8:50.
We northeners aren't used to the currency fluctuations when we venture from home.?

Have been to British museum several times but judging by the response the Wellcome collection sounds well worth a visit.

Suzied the park idea is excellent as will definitely be good before a flight. Fingers crossed for good weather.

Many thanks for your input everyone.

Assuming that you'll be leaving your luggage at the hotel and will travel from there to Heathrow, you don't want to be too far out of the Kings Cross area on a busy Saturday afternoon!

If it's park weather, Regent's Park is about a 20-minute walk - you can admire the wonderful Nash architecture on the approach.

Yes around Kings Cross has been redeveloped and there lots of interesting squares and little parks - I agree with river walk - go along Regents Canal to Regents Park a lovely walk. You can see loads of pretty houseboats and there’s a new little nature reserve there , also the back of the zoo, Snowden aviary. There’s a cafe in the park. Fingers crossed for good weather, I know before a flight you’re always a bit restless so nice to be outside before all the hanging about at the airport...

Somewhere special for afternoon tea? A lovely start to what sounds like a wonderful holiday. Would probably need to pre book a table though. Check online for places. The ritz and so on are the other side of town but there will be others closer.

Go to St Pancras and book tea at the St Panrcas Renaissance hotel. Very expensive but if it is as good as the food and service in the hotel's Gilbert Scott restaurant, where I was fortunate enough to be taken out to lunch last year, worth every penny.

There is of course the champagne bar at St Pancras...

You could drink standing up OP ( you said you didn’t want to do anything sitting down)

Stay within walking distance of your luggage- so much can go wrong with all forms of transport and the last thing you want is to be feeling anxious.

The British museum is within walking distance but you can get the no. 73 bus opposite St. Pancras.

I’m trying to avoid anything involving food and drink as we are going on holiday with friends and think there will be lots of that when we get there? I’ve suggested we do the walk along the canal if the weather is dry and the Wellcome collection if it’s wet.