A man has plead guilty to attempted robbery with an imaginary weapon, having threatened a bank cashier with a drawing of a gun.

The 33-year-old Briton entered the bank on Jerozilimskie Avenue bank in Warsaw, Poland on August 11, before walking up to a cashier's desk, and demanding she hand over money.

Because he could not speak Polish, the man prepared a number of cards. One had a picture he had drawn of a gun; another, the phrase "This is a robbery. I have gun. Give me the money," written in Polish.

According to the Telegraph, bank cashier Agnieszka Wlodarska was unphased by the cartoon threat and simply asked him to wait his turn at the rear of the queue.

Following her instructions, the man sat down with other customers while she called police.

“At no time did he speak and did not behave aggressively,” said Ms Wlodarska.

Police arrived shortly after and arrested the man, who has since plead guilty to attempted robbery.

The man, who cannot be named due to reporting restrictions, had been resident in Germany for a year and had only arrived in Poland hours earlier.

He faces a maximum sentence of 12 years in prison.