It is believed May could be thinking of triggering article 50 on Tuesday, if the bill clears parliament smoothly the day before. There is speculation that if Tuesday proves impossible, the process could be shifted back until later in the month. This would have cleared the way for May to have announced the start of the article 50 process at a summit in Brussels on Thursday. The article bill thus returns to the Commons on Monday afternoon for a process known – officially as well as in practice – as “ping pong”. How long this process takes could be key to the article 50 timetable.

Source: The Guardian March 12, 2017 16:13 UTC