Christmas in London is worth the trip. It's also a lot to plan. The lights go up in early November, every market opens on a different date, the best tickets sell out weeks ahead, and on 25 December the Tube doesn't run at all.
Our London Christmas Guide puts it all in one 23 page PDF with links to book shows and attractions. It covers which markets are worth your time, a walking route for the lights, what to book first, and how to get through Christmas Day when most of the city is closed.

Most lists of things to do in London at Christmas give you forty ideas and no way to choose. We'd rather tell you what we'd pick. On a first visit, start at the Southbank Winter Market. With kids, go to Winter Wonderland. For the view, walk to Winter by the River beside Tower Bridge.
The guide works the same way all the way through. It compares the options, says which one fits which kind of trip, and groups things that are close together so you aren't zigzagging across the city in the cold.
The guide covers each one and tells you what to do instead.

This guide is all about the festive side of London. For airport transfers, the Tube, neighborhoods, everyday sightseeing and restaurants, use our London Travel Guide. Together they cover the whole trip.

Yes, especially from late November to mid-December. The lights, markets and rinks are all open then, and weekdays are much quieter than December weekends.
Very little. Most attractions, museums, markets and shops close. Churches, parks, some pubs and hotel restaurants stay open. The guide has a full Christmas Day section, including where to eat and how to get around.
Most switched on in early November. Regent Street lit up on 5 November, Oxford Street on 9 November and Covent Garden on 12 November. The Trafalgar Square tree is lit on 3 December.
Our top picks is the Hyde Park Winter Wonderland. The guide compares 17+ markets side by side.
Right after you buy it. It's a standard PDF, so it opens on your phone, tablet or laptop, and you don't need an app.
Only the festive side. For everything else, pair it with our London Travel Guide.