Alternative Ending:
Two months later, Jack, in his first suit in centuries, stood outside the hall in the shadows as Ianto and the enemy stood at the alter.
"We are gathered here to day to witness the union of Ianto Jones and Elian Myers." The man at the alter said, "Who gives this man to this man?"
"We do," said Tosh and Rhiannon, Ianto's sister.
"Who gives this man to this man?"
Two unknown people said "We do."
"Does anyone hear have just cause that these men should not be joined together?" The man paused. "Speak now or forever hold your silence."
Jack yearned to object and to call out stop, please, Ianto give me another chance. But the words would not come. How could they when Ianto looked so happy?
Jack turned away, not wanting to see anymore. He walked away into the rain of Wales, his heart with Ianto. He got the box out from under his bed and took out the perfect ring. He climbed again to the tallest building and cursed his stupidity and his insecurity. It had cost him the one person who made him whole. Jack kept no track of the hours as the rain came down on Cardiff.
Jack heard the door of the roof swing open and footsteps coming close.
"I'm in no mood, Tosh."
"I'm not Tosh." Jack whirled around at the sound of Ianto's voice. "I knew I would find you here."
"But, you're suppose to be getting married."
"I couldn't say I do. As I stood there at the alter, I could only think of you. I couldn't marry Elian because my heart was with you."
They were silent for a time, both looking out onto the bay.
"Why did you do it? All those years ago, just tell me why?"
"Someone confirmed my doubts about what I could give you and I let all the cons cloud my judgment. I wanted you to be happy and to have someone to grow old with and we both know I can't do that with you."
"I don't care, Jack," His name rolling off Ianto's tongue for the first time in five years, one month, two weeks, and four days. "I don't have but a small window of time to spend with you. Don't waste that just because we can't have forever. I've spent five years of my life trying to pick up the pieces left behind after what you said. I don't think I can ever recover. Please, let me make my choice. I want you for now and for the rest of my life."
"You know for two weeks before the incident, I walked around with this in my pocket." Jack pulled the ring out and showed it to Ianto, "Tosh helped me pick it out. It's a Welsh knot. I wanted to marry you so badly. You have no idea how much."
"I think I do because I want to marry you too. Forget regret or our time together is yours to miss. Let's love for as long as we can."
"Okay, we will. I'll wait forever for you."
"I love you, Jack Harkness."
"And I love you, Ianto Jones."
And they both lived happily ever before, which is the same as after just in reverse.