When we site a marquee, even if it has a suspended wooden floor, we drive home 1m long metal ground stakes. One in each foot. The recommended loading should be 600kg of upward pull to move the leg once the stake is in place. So if we site a 12m x 24m tent the total loading should be 24 ( legs !) lots of 600Kg = 14,400 Kgs. If you want to see what can happen if one takes off simply look on YouTube where you will see several examples. Bare in mind that a 12m wide marquee itself will weigh probably 2 tons when it is fully sheeted and lined. It can cause serious damage if it becomes detached.
Courtesy of YouTube: A video link below of a 12m structure in Hampshire tossed about in the wind. Doesn't look pined - but difficult to say .
If you are concerned about the danger of your marquee taking off then you can always consider buying Event Insurance. This typically costs about £100 for the average banquet bash for 100 guests and will include other cover that may be important to you such as cancellation, damage waiver, personal injury etc..