Palmerston, the Foreign Office's resident cat, caught his first mouse on Tuesday.
The black-and-white feline moved into Whitehall last month after his successful his application to become Chief Mouser.
Palmerston retweeted a post from Simon McDonald which announced that the cat had caught his first mouse in the early hours.
His post read: "The 2nd biggest news story @foreignoffice is that @DiploMog has caught his 1st mouse! Btw, congratulations @LCFC.