The Bimek SLV is implanted in the spermatic ducts with a rocker switch - which can be located easily by hand through the thin skin of the scrotum - and turned on and off.

In its closed state the valve prevents sperm cells from leaving the testicles and mixing with the semen before ejaculate, and, like a vasectomy, the sperm is instead reabsorbed into the body.

The difference, however, is of course that while vasectomies cannot always be reversed, the Bimek SLV allows a man to "turn" his fertility back on whenever he likes.

Note: The makers warn it will take between three and six months for men to get rid of any lingering sperm cells in the seminal glands or prostate, so additional protection would be needed initially if used as a contraceptive.

Switching it back the other way, however, should give immediate results as the body does not take a break from producing sperm cells.