Destinations from London

I don't know that you want to spend the night there, but Dover is my favorite castle because I can really see it as a defensive fortress rather than a palace.

Portsmouth, if you like British naval history including Lord Nelson's flagship, Victory, naval museums, the restored Mary Rose, Henry VIII's flagship, great waterfront shops and pubs. We spent two nights there awaiting our ferry over to France. Closer and easier is Greenwich, with the Prime Meridian and Greenwich Mean time, the history of finding longitude using clocks invented by John Harrison, the Greenwich Royal Observatory, Royal museums,the Cutty Sark, and there is a large market on specific days, I forget which. Don't miss eating whitebait, a house specialty, at the Lord Nelson Tavern, right on the riverbank. Great history at both and great walking opportunities as well.

Bletchley Park is fascinating if you're interested in WWII.

Spend one day at Blenheim Palace and one day in Oxford. They're both gorgeous with lots of history. Consider staying at Corncroft Guest House, a B&B in a renovated 200+-year-old stone building, in Witney. The included full English breakfast is excellent. Witney is picturesque and fun to walk around, and includes a 13th century church. You can easily walk to pubs, restaurants, shops, and even a highly-rated brewery tour.

Bath/Cotswalds

You could go directly from St. Pancras to Paddington for the train to Bath.

P.S. Go Gators

Windsor and Eton (5 minute walk between the two towns), Bath

Historic York is perfect for 2 days - the charm of walking on city walls restored by Queen Victoria; touring the stunning Minster & Tower, enjoying a city tour of the Shambles area, and bragging about drinking at the Guy Fawkes Pub. There are several B&B's near the train station just outside the walls. We've stayed at the historic Grange Hotel (a bit of a walk to the walls) and Rick's choice, Abbeyfields. Enjoyed them both.

Ray,

If you're mostly interested in "history, military", it may be difficult to find a place that keeps both of you happy. You could take day trips from London or spend the two days somewhere else and just return to London the night prior to your flight home. If you'd prefer to stay closer to London and take day trips, you could perhaps visit the famous Tank Museum at Bovington (Dorset). They have an incredible collection of armoured vehicles, including the world's only fully restored and operational Tiger tank (which was used for the first time in the movie Fury). Makes quite a racket when it's running! The closest rail station appears to be Wool, and I'm not sure how to get from there to the Museum. I've had a rental car on the occasions when I've visited.

As mentioned in the previous reply you could consider a few days in York, as it's a beautiful and historic city. You could tour "The Shambles" and of course the amazing York Minster. There's also an incredible Railway Museum there, which is "free" as I recall. The local walking tours provide an interesting glimpse of the history. For WW-II history you could make a day trip to Eden Camp, which was voted one of Britain's top attractions several times. It was originally a POW camp for German and Italian prisoners, and you could easily spend the better part of a day there. You'll have to check on transportation from York (I'm sure there's a Bus or something?). I used a rental car so getting there wasn't a problem.

Have you seen all the Museums and other military sights in London (IWM, HMS Belfast, Churchill War Rooms). There's also the RAF Museum at Hendon, which you can reach by Tube (disembark at Colindale, not Hendon). Again, you could spend the better part of a day there as it's bigger than it looks at first glance.

There's also the Fleet Air Arm Museum at Yeovilton, but that's probably a bit too far from London and with such a short time frame.

Finally, as Chani mentioned, Bletchley Park is an easy day trip from London (about an hour each way by train). The story of the code breaking is absolutely mind boggling, and watching one of the Bombe computers in action is fascinating.

We loved both Bath and York. The Roman baths in Bath have about the best audio guide I've experienced. Normally I give up on them by half way through, but not this time. And my husband was totally enthralled. It was a pleasant bus ride from Heathrow. And we also loved walking along the canal. York was also amazing. We took one of the free tours and gained so much history before walking the wall ourselves. The York Museum was a nice little gem -- not too busy (but I recall we both fell asleep in the little movie theater so I guess we were tired). One last item -- if you are into the history of air force, then I suggest the Imperial War Museum at Duxford, outside Cambridge. It is filled with all types of airplanes, tanks etc. There is even a large exhibit for American planes, and a great deal of appreciation for air support the Americans provided during WW II. Not too easy to get to, but you might check it out.

We really enjoyed York, I think it was only about a 2 hour train ride from London. Walkable, the Minster was very nice, a nice little park area.

PPS- Go Gators too! ~,==,<

I'm fond of Winchester and it is an hour on the train from Waterloo. Google and see if it fits your bill.