4.5 hours in London-what would you do?

I d go to the top of a very tall building of which there are several to choose from

You don’t have to face the scrum at Fortnums, they’ve got a shop in St Pancras station which is infinitely more civilised and a five minute walk from Euston.

Regent’s Park would be lovely - you can rent a pedalo there. It sounds like you’ve already got lots to fill the time.
the British Museum and Coram’s Fields are nearby too.

I think what you're doing is plenty. I would probably ditch Covent Garden if you want to do Fortnums, Green Park AND Regents Park. I would head from Lego towards Piccadilly and walk along to Fortnums (pop into Hatchards or Waterstones for a quick book browse - good kids sections. Probably some Lego books!)

There are ice cream places along Piccadilly (Venchi for eg) or inside Fortnums, where you could stop for an early ice cream lunch! They also have the new Biscuitorium which is kind of fun - lots of nice biscuity things to look at, some buttons to press. It's an easy tube from Green Park to Warren St for the hospital, or you could walk on and dip into Regents Park.

I would stay on foot and have a wander from Leicester Square to Trafalgar Square then duck into the National Gallery and catch up with one or two paintings. Or if that doesn’t appeal, National Portrait Gallery for a targeted visit - must be someone the family loves whose portrait is there - maybe from sport or music?

Then I’d head towards Covent Garden via Seven Dials, maybe have a look in at Neal’s Yard. I wouldn’t go to Forbidden Planet personally, but I have friends who would love it.

Seven Dials Market could be good to drop into if anyone needs the loo or to cool down, have a drink.

If you’re going to Fortnums anyway book the icecream parlour there - it’s very good!

sone of these suggestions are crazy and would take a full weekend!! If you’re at Portland then of course go over to Regent’s Park, there’s plenty in there, walk up past the zoo to Primrose Hill then to Chalk Farm and to Camden Town market / lock etc, along the canal and back again. Plenty of lunch options, views, cool shops and sights en route.

@mrshohoif you Harry Potter there is a place called Mina Lima near Leicester Square. It is a shop come mini museum that has original artwork from films. It’s very very far from a Harry Potter tourist shop.

I would avoid F&M like the plague. It's always RAMMED, intensely overstimulating and scary for children. Tourists going wild over tins of biscuits and mediocre chocolate - it's the pits.

Have you been to the Lego store before? If you've been once, it's not worth going back dor another visit imo.

With that time and your kids' ages I'd either do the British Museum/Zoology museum straight from the station, or do South Kensington and the National History Museum/Science museum.

Battersea Power Station really isn’t all that IMO. I’d go to the Wellcome Collection and then walk into Bloomsbury; a lovely part of town and quieter than many central areas. I’m sure you’ll find a nice ice cream place there.

Cabinet War Rooms (now called Churchill War Rooms I think) is also excellent - echo a PP that this is a great plan if interested in the War or DC are studying it, and it’s near St James’s Park and Parliament.

Have you done London and the big sites before? If not, sack off all the commercial tat you have planned (buy Lego online and ditch the cinnamon bun place) and go somewhere like The Tower of London, or do an open top bus tour or one of the river boats with really good commentary.

Or I’d go to St James’s Park, look at Buckingham Palace from the outside (see if your timings work to see the changing of the guard), walk through the park to Horseguards (stop and look at the pelicans), get an ice cream en route, go along Whitehall to see Big Ben and Parliament then do Westminster Abbey or go back up Whitehall and see Trafalgar Square before heading to Covent Garden.

I second this, or the Grant Museum of Zoology is a few minutes walk. Love a jar of moles.

I'd give a whole day for Battersea. The op would have less than 3 hours and with kids in toe who wants a mad scramble to make it back to the appointment.

Battersea power station is a great shout. You can get the northern line from Euston and back to Warren Street for the Portland. Really cool Lego store plus great architecture and you can go up one of the towers on the tour.

Wellcome Collection on Euston Rd might be appropriate

I must do this some time!

Lots of good tips on here that I’ll do myself at some point!

Cabinet War Rooms, off Whitehall is an option

Regents Park is also a great shout - I haven’t been there nearly as often as I should! TBH I don’t know that area very well. Don’t think I totally took in which hospital you were going to on first reading of your OP.

We do love Lego too! In fact I have been looking at how we might go to Legoland Billind and the Lego house some day… So definitely not at all immune to its charms.

Science museums (or any of the museums) is definitely an all day event, I agree. But very well worth it! My tip for those would be to definitely bring a packed lunch.

I will come to you for tips if I’m in Manchester without a specific purpose like work or taking DD to look at the Uni (as we did last week) as I always feel like I’ve probably not seen much of the place beyond the very surface level! (Don’t worry I don’t actually plan to DM you!)

I would go to Battersea power station if I were you it’s quite cool, you can go up the chimney for views have great shops and restaurants including a Lego store

Regents park is ideal after your shopping and son close to the hospital. The boating lake is fun. It's hot and sticky in London but lovely in the parks.

Why not go along to London dungeon or the eye?
A river cruise
A museum?

The Lego store really isn't all that if you've been before. Very little you can't just get online.