Where to leave/drop our bags last day in London

It's my understanding that museums are happy to accept day packs but many of them cannot accommodate larger bags.

The left luggage facility at St Pancras International is staffed (no lockers). The size of the bags is immaterial. Here's a quote from the St Pancras International site: "Excess Baggage provides a secure left luggage facility and is located at street level in the Circle area of the station, just past the UK Rail ticket office. Opening hours are 06:00 to 22:00 Monday to Saturday and 07:00 to 22:00 on Sunday. The cost is £8.00 per item (of any size) per 24 hours, therefore your item can be stored overnight if needed."

Answering my own question (sort of). It appears that the British library has lockers that we can use, that are essentially free (you pay £1.00 and get the deposit returned when you take your bags).

Has anyone used this recently, who can confirm?

We visited the British Library on June 13. While we did not use the lockers (we used the Kings Cross left luggage--8 pounds per bag), I did check them out for future reference. They appeared large enough for day packs but they would not hold a full size backpack or suitcase. What day are you travelling? We were there on a Sunday when only the exhibits are open--people were carrying small packs and wheeling small carry-ons. However, I believe this is only allowed on Sundays. I was also advised that most of the lockers are taken on weekdays.

I don't know about the British Museum--I have never visited it on a day when I had luggage.

I would get to the Eurostar one hour ahead--it has airport type security -for check-in.

http://www.tripadvisor.com/ShowTopic-g186338-i17-k2098901-Left_luggage_at_euston_or_waterloo-London_England.html

The above thread from tripadvisor (two years' old at this point) suggest that carry-on-sized backpacks should fit in the lockers which the poster says are 28in x 14in x 16in.

however, if they are all taken, the size is irrelevant.

We are traveling on a Tuesday in late August.

I'm trying to avoid two things: backtracking and expense. If I drop the bags at St. Pancras, then I'm spending about $25 and then backtracking to the museums.

I may just check my bag at the British Museum (their website says large luggage is £1 per item) and then take my chances checking in the lockers at the Library.

Doing this will avoid backtracking (saving time) and minimize expense, although it will increase our burden, since we'll be lugging the backpacks from hotel -> Museum -> Library -> Station.

No perfect way to do it I guess. All options have pros and cons.

For the museum, if you go in the back door (not Great Russel Street, but the parallel one behind the museum) there a spot to check large stuff. I didn't do it, but noticed there was a price -- maybe a pound.

Like Tim said, going in the front door you can only ditch what I'd call daypack size. I've never done that either.

The library is too far back for me to remember.

Here's what I found on the British Museum site.

Cloakrooms: The main cloakroom is to the west of the Main entrance. There is another at the North entrance. £1.50 per item, 50 pence for umbrellas, fold-up pushchairs free. Maximum size: 40x40x50cm Maximum weight: 8kg (except fold-up pushchairs)

Luggage restrictions: Please do not bring large bags or suitcases to the Museum. Items larger than 40x40x50cm are not allowed on the British Museum premises for safety and security reasons.

I think my 14x22x10 Eagle Creek bag should be ok under those guidelines.

The British Library is just down the street from St Pancras. The Museum isn't quite so close.

Not to be contrary, but while you can "see" the British Museum in a few hours, it really merits a full day. It's huge, and fascinating. Seeing both the Museum and the Library in one morning doesn't seem to be worth the effort or the risk.

If it was me, I would be inclined to spend my morning at the British Library, having lunch at their rather decent cafe. Then I'd walk down to St. Pancras and get on the train. That would make for a nice, relaxing, morning with no worries about missing the train.

I'm actually entering and departing London via St. Pancras. Maybe I'll make the British Museum our first stop off the Eurostar, and then hit the Library on the way out (or vice-versa).