Jet lag happens when you cross time lines and your body gets confused as to whether it is day or night. For example, going to London from Texas takes about nine hours in the air. The clock in Texas said something like 4:00 PM on take off and the clock in London said something like 6:00 AM on landing at Gatwick. Jet lag happens when you can't sleep on the plane-which I could not-and its the start of a new day when you arrive.
The Travel Insider has a lot of advice about the treatment of Jet Lag-get a lot of sunlight during the day and take Melatonin at night. For me Jet Lag mainly means that the first day in London is pretty much a wash. Staggering off the 777, finding our way through Customs, getting on the Gatwick Express, navigating The Tube to get to the Hotel and then-well, it all becomes a blur.
Drinking lot of water is always good advice and try not to think about what time it is at home. A quick search on Amazon gets over 600 results for Jet Lag and a Goolge Search gets over 600,000 results. My own method of dealing with Jet Lag was to drink lots of water and try not to sleep until it was night time in London. I would not advise having anything really important to do on that first day. We wandered around the British Museum, an amazing place even when you are half asleep.
Do the many cures for jet lag work? I don't know. I do know that I was totally exhausted by the time our plane landed. Of course, that first flight we had seats over the wing with a nice view of the giant jet engine out the window. My advice is to get a seat as close to the front of the plane as you can and drink lots of water.
Just be aware that the first day in London could be a bit tough. The following days were better. There is so much to do and see in London that you'll be tired at the end of day. Then you'll sleep at night and feel fine-just in time to get back on the plane and head back home. I don't recall a lot of jet lag on the return home-but then, it is always good to be home.