The HM Treasury name is seen painted on the outside of Britain's Treasury building in central London, Britain November 25, 2015. REUTERS/Suzanne Plunkett

LONDON (Reuters) - Twenty-two mice scurrying around Britain’s finance ministry have fallen foul of the chief mouser to the Treasury since he took up residence one year ago with a mission to reduce the government department’s rodent population.

Gladstone - a black cat named after long-serving 19th century prime minister and chancellor William Gladstone - joined the Treasury from a rescue home a year ago, and has almost 10,000 followers on photo-sharing website Instagram.

“I’m a grafter! This last year I’ve caught 22 mice and I believe in going the extra mile, so I’ve also caught 2 flies – it’s harder than it looks!” Gladstone said in a message on Friday to mark one year since he joined the finance ministry.

Finance ministry officials, who manage Gladstone’s social media presence, regularly post photos of him wearing brightly colored bow-ties to mark events such as gay rights celebrations, the introduction of a new 1 pound coin and visits by foreign dignitaries.

Gladstone said the visitor he was most looking forward to was International Monetary Fund managing director Christine Lagarde, who is due in London later this year.

“Until then I’ll settle for the Chancellor. For a dog person, he’s very amenable,” Gladstone said.

Gladstone declined to be drawn on reports of rivalry with other senior government felines such as Larry - who lives in Prime Minister Theresa May’s office - and the foreign office’s Palmerston.

“When columnists try to pit you against other Whitehall felines, stand tall - you’re the top cat. That, and black is always slimming,” he said.