We leave the EU at 11 pm on Friday. Big Ben will likely not, as far as I understand, be bonging.
We then enter the transition period, under which everything continues as usual until the end of 2020 (except for NI?), at which point we will either i) have a full FTA agreed and signed and we’re on our way to the sunlit uplands; ii) we request an extension to the transition period, which Boris has said will absolutely 100% not be happening, and he seems like a trustworthy fellow to me; or iii) no deal/goo spoons