At least he didn't have to convince River that it was really him. She, with her clever mental fingers, could sift through his mind and find out for herself. Probably already had, in fact.
When she threw herself at him, Ianto caught her, holding her steady while she examined him critically. She must have been satisfied with what she saw because that's when the release came. Instead of taking her inside, Ianto crumpled to the damp ground and settling her on his lap so that bare feet rested on thin air and not wet grass. "I know," he murmured. "I know, I'm sorry, I didn't want to go. I'm here, I'm here."