As patron of the charity, Simon Cowell was due to host the Together For Short Lives midsummer ball on Wednesday evening with his partner Lauren Silverman.
Unfortunately he wasn't well enough to attend, his spokesperson confirming he was laid up in bed with flu.
Simon is patron of the charity and had been looking forward to raising money for young people with life-limiting and life-threatening conditions.
But he has been suffering so badly with a bug over the last few days he has been unable to leave his home in the capital.
A source close to him told the Mirror: “He wouldn’t miss this event unless he was feeling really ill, the charity means a great deal to him.”
Friends say the workaholic had been pushing himself to the limit on Britain’s Got Talent last week both on the panel and behind the scenes helping producers.
Get well soon Simon x
