DISCLAIMER: Harry Potter is owned by JK Rowling. I'm just playing with her world.
Vernon Dursey may have been a big man, but no one could have ever called him slow or lazy. If someone were polite, they might have called him "energetic." A more accurate term would have been "hyper." His first love was boxing, but realizing as a young man how few amateurs actually make it to the pros, he applied the same energy to more intellectual pursuits and soon found himself working towards a degree in mechanical engineering. Soon after graduating he found a job as a junior engineer at a manufacturer of machine tools called Grunnings. His jovial, energetic personality endeared him to Grunning's customers, and attracted the attention of his bosses who soon transferred him to Sales Engineering. It was here that Vernon really took off, so to speak, and in a few short years he became one of Grunning's top employees.
Boxing however remained a hobby of his, and after work he could often be found at the local gym keeping in form. One of his sparring partners and friends was a detective from Scotland Yard named James Potter. James was just as energetic as Vernon, and despite being half Vernon's size gave him a run for his money in the ring. One evening at a party, Vernon was introduced to James' sister-in-law, Petunia Evans. It was love at first sight, and soon they were married.
Increasing demands on their time from both the job and the family kept James and Vernon from visiting the gym as often as they'd like. Vernon was promoted to manager of the Sales Engineering department and moved to Little Whinging. James transferred from Scotland Yard to MI5 and moved to the West Country. The two families both had a son. James and Lily named their son Harold. Vernon and Petunia named theirs Dudley. During the party after Harry's baptism, Vernon and James got together for a drink. James was looking rather frazzled. "Rough time at work?" Vernon asked. "Can't really talk about it, but yes." James replied. When Vernon said "The Provos." James just nodded. Vernon read about the problems in Northern Ireland and assumed his friend would be working on it. They both promised each other they'd get together again soon for a sparring match in the ring. Vernon was getting a little soft, and he thought James needed to blow some tension off. Little did they know that would be the last time they would see each other.