-- wizard in plus-fours (GF7)
A Ministry wizard dressed in Muggle plus-fours was in charge of making sure that owners of the campgrounds at the 1994 Quidditch World Cup tournament did not notice the magic activity going on all around them. He did this by casting multiple Memory Modifying Charms on them. It was an exhausting, non-stop, difficult task and “his chin was blue with stubble and there were deep purple shadows under his eyes” (GF7).
Plus-fours are a type of men's trouser that is four inches below the knee. The look is a bit old-fashioned and they were usually associated with sports attire worn for Muggle golf, cycling or game shooting (Wikipedia).
As he was on duty while working at the Quidditch World Cup in 1994, it is likely that he was among the Ministry employees that fought against the Death Eaters during the chaotic events in the campground after the match (GF7).
Lexicon list of Ministry of Magic employees
From the Web
Pottermore feature (a mention of plus-fours): Dressing for kicks in the Twenties
Harry Potter Wiki: Roberts's Obliviator