Holly Willoughby was left blushing pink as her private joke about "self-pleasure" was unveiled on Tuesday's episode of This Morning.The 41-year-old TV star was caught off-guard as the camera continued to roll as she chuckled away with TV doctor Zoe Williams.As the lens returned to the twosome, they couldn't hide their giggles and were asked by co-host Phillip Schofield to disclose what had been so funny.Unable able to share the joke, Holly said: "Sorry, we're just laughing because..."Excited TV star Phil chirped in: "Ohh I can't wait for this.