With Teresa May announcing that Article 50 will not be evoked until the end of the year Britain faces more uncertainty. As capital knows no loyalty or favours it will always go where the greatest opportunities lie and uncertainty is unfortunately the most unattractive thing to capital. This is one contributory factor to further short selling of the pound in the near term.
The interest rate will likely be cut again soon (from the current all time low since 2009) and that seems to have already been factored into the market. The Bank of England will likely engage in more Quantitative Easing (which means money printing to us). Both of these initiatives will put further pressure on the pound.
The political and economic environments do spell further downard movement for the pound in the short term.