An inquiry will be held after hundreds of voters were turned away from polling stations and police called to deal with queues as the voting deadline passed.
But at many other stations, the voting process ran smoothly. Below, Susanna, a polling clerk in Sheffield, tells the story of her day.
It is just about midnight on Thursday and I'm only recently home from the polling station.
Democracy in action. And what a day it's been. My first ever stint as a polling clerk. I got up at 5am, set up the station with the presiding officer, signs, booths, paperwork etc. and was all set to open at 7am. A brisk morning ensued, people on the doorstep as soon as we opened.
A lull of about 45 minutes at lunchtime and then all hell broke loose. For about six hours we had no time to get a drink or even go to the loo.
Queues waiting patiently, people coming from playing football in their kit, all hot and sweaty, people struggling through wind and rain, rushing over in their lunch hour, straight from their shifts, straight from work etc.
There were lots of people of all ages and backgrounds, the very old, the very young, and all in between. With one set determination: to be heard.
A polling station in Hackney. Elsewhere in the borough there was chaos
We had two inspections from the voting inspectors to check that everything was being done legally and two more phone calls from them. We had two sets of party agents come in to shake our hands and ask how things were going.
Then two policemen came in, in uniform, and I asked them if they had come to vote. They and the presiding officer laughed: they had come in an official capacity to check that everything was legal and that we were not having any problems.
Often the voters did not know who to vote for, but they were determined to vote. That was all they could do: lots of mentions of the people who had struggled and died to get the vote and how serious this was. Masses of students, whole housefuls who came together, excited and enthused, voting for the first time. Punching the air, punching the table - "this is us, listen to us". But will anyone listen?
Then the sad people who stood outside the booths saying we want to vote but there is no one worth voting for. Dithering, walking up and down outside several times trying to work out what to do before coming in: one lady who pulled her voting slips back out of the ballot box saying she had changed her mind, asked for a rubber and redid her vote.
This was powerful: decent people who had had enough. They probably would have disagreed on who to vote for, but they all believed in democracy, wanted to do their bit, but wanted our leaders to be honest and to represent THEM. It was very powerful and very inspiring.
At this polling station in Dalston, London, things did not run as smoothly
I did a quick calculation and we had over 70% of the voters in our ward come to the polling station and vote.
For my first time as a polling clerk it could not have been more thrilling. When the presiding officer told me that he had a police escort to enable him to get the votes safely to the count and to prevent then being tampered with or anyone infiltrating a bomb or other security risk I was thrilled.
I passed this on to several of the young people, to show how valuable their votes were considered to be, and they were so pleased it was really touching.
What a day! My presiding officer suggested I applied to be a presiding officer next time and perhaps I shall. Then I will have the police escort!! And not for doing anything wrong.