Australian Silver Gull, Chroicocephalus novaehollandiae, (Australia was once known to the world as New Holland). More commonly known as seagull, the correct name of silver gull is more appropriate as they inhabit inland areas as well as coastal, and are as happy in carparks, tips and sports grounds as anywhere near water.
Legs and beaks range between black and bright red.
Just read your comments- sounds like the Ring-Billed Gull that we have. It's also commonly referred to as a seagull & they can be found in the same type of locations as your Australian Silver Gull.
Nice eye!