I know of a horrific fall out a (outing to say how) huge wedding that went ahead and blew apart at the wedding reception. I'm trying to summarise it without giving my role in this away - it's long and I apologise in advance for how I've written it 
The bride and groom were childhood sweethearts. Dream Wedding planned etc
The bride a lovely sweet sweet girl who adored him. Bride works in her home town - really local and family oriented. He was the centre of her universe.
Groom (utter cockwaffle) worked in the "big Smoke" city in finance had a secret girlfriend of several years. These two women knew nothing of each other. He was having his cake and eating it.
We know now that he Spent the hen do on a weekend away shagging with the secret girlfriend. Utter scum bag
Secret girlfriends family and friends were suspicious of groom after 2 1/2 years of a relationship (didn't have social media and she had never met his parents hung out with friends etc) he made little effort and they never saw him. He was always polite but very discreet.
After a bit of stalking, the secret girlfriends family somehow found out about the Wedding and obtained a copy of the invitation. (I can't say as very outing)
Secret Girlfriend confronted groom over the phone and he said that the bride (he said she was his crazy ex-girlfriend) was mental and it wasn't true and not to believe anything her friends were telling her.
After long conversations he finally admitted that he was due to be getting married a few days later to his childhood sweetheart and that he had been carrying both poor women along for several years.
Said he was ashamed of himself blah blah blah please don't leave me etc
The night before the "wedding" he told secret girlfriend that he'd called it off and he then sent her lots and lots of dick pics saying that he wished he could be with her etc
The following Morning he was non-contactable. By that Point it was pretty obvious to secret girlfriend that the wedding was going ahead and he was a total bastard.
Secret Girlfriend told her family and friends. Secret girlfriend still had a partial copy of the wedding invitation.
Secret girlfriends father was livid, got in the car and drove all the way to the (what was now) evening reception in a rage found the bride and told her everything. She didn't believe him. Asked him who he was, very confused.
The girlfriend and her family had followed father there in a convoy, concerned at what he was going to do. (The girlfriend at this point was distressed and wanted to stop the father) anyway they arrive separately and the groom clocked the girlfriend as soon as she walked in the room and manhandled her into the garden ( he had no idea that poor bride was already being informed by aforementioned father in another corner of the room- as he had never met him, idiot didn't know what secret girlfriends dad looked like!!)
Bridesmaids soon realised what was happening- absolute chaos and horrid name calling and accusations flying around. Everyone staring
Bride is naturally and quite rightly so completely devastated and doesn't believe it until secret girlfriend produced evidence - calling his secret second phone, produced photos of them on holiday, dick picks (vomit) other outing things like signet rings and his clothes he had left at hers.... it was undeniable.
Bride realised it was true, punched him, demanded car keys from someone (can't remember who) and got in a car and drove off.
Secret girlfriend and family made swift exit.
Next day groom calls secret girlfriend asking for her to take him back.
She declined!
Secret girlfriend tried hard to contact bride and apologise for ruining her day but it didn't yield any response (understandable!)
I believe that the bride took him
Back, that they had children and have very recently divorced.
I am neither secret gf or the bride, I just wanted to write this in a way that didn't give too much away as it was really traumatic for both women who were deceived.
I think of them both often and hope they are ok.