This photograph (008263D) from SLWA’s online pictorial collection comes from the 1950 Foundation Day celebration. Sir James Mitchell is inspecting a Naval Guard of Honour. Mitchell was the Governor of Western Australia, as well as the former premier. He died the next year, one month after retiring from office.
According to the Department of Employment and Consumer Protection:
Foundation Day is a uniquely Western Australian public holiday. It commemorates the day that the first European settlers arrived in Western Australia to found the Swan River Colony on 1 June 1829. Foundation Day is held on the first Monday in June each year.