Alan had grown suspicious when he noticed Kaspars giving his wife lifts to work. Eventually his wife admitted to the affair and then kicked Alan out of the house so she could move the new man in.
The most disturbing thing about this is the photos that appeared in the Daily Mail. Notice how Lisa is wearing the same fucking clothes and there are the same trees in both shots? It's because they are in the same location. This suggests that Alan had to show up and pose with his family and ridiculous tattoo before his wife went to pose with the dude she left him for. Hey, the paper had to finish their story, and Kaspars's career as a fitness instructor could use the free publicity that banging another man's wife might bring.