Very recently, Transport for London published that some of the Tube lines will be available in 24 hours. From September 2015, we can utilize the Jubilee, Victoria and a part of the Piccadilly, Central and Northern lines on Friday and Saturday night.
Currently, from 1 to 5 O'clock we cannot enter the underground. If the Night Tube plan is realized, the situation will be considerably changed.
First of all, we will not need to worry about the final train when attending a dinner party on the weekend. It is a common desire for drinkers regardless of the countries. Second, the midnight administration of the railways will vitalize the industry around the regions. Of course, more employment is required.
There will be a need for 24 hour stores in the stations. Unfortunately, current space of underground stations is limited. Some stations are to be considered of reformation.
In Tokyo, many homeless persons gathered under the subways where anyone could stay regardless of the time. Since it was deemed to cause exacerbation of safety, the metropolitan police had to deal with them. The same issue may occur in London.
I am not sure whether this decision will make a profit for the railway company. Ironically, I seldom use Tube, because the buses are less expensive.