Billy Vunipola has discovered that breaking his arm three times in ten months was down to more than misfortune. The Saracens medical team launched an investigation after the England No 8’s most recent injury, suffered against Glasgow Warriors in October, and tests revealed that a vitamin D deficiency due to a lack of sun on his tanned Tongan skin contributed to the succession of forearm fractures.

Vunipola, who made his latest comeback in Saracens’ defeat by Sale Sharks on Friday night, is now under orders to take daily vitamin D supplements, drink more milk and he is even permitted to indulge in his favourite camembert, within reason, to help strengthen his bones.

The 26-year-old suffered the first injury playing for Saracens in January last year