Every time somebody always says head gasket. If the anti freeze is able to leak into the cylinders through a bad gasket what do you think will happen when the engine starts? With over a hundred pounds of compression don't you think it would leak back through that head gasket and blow off the radiator cap?

Most likely a cold water leak at the intake manifold gasket. I'm not sure your engine has a throttle body that is water cooled but that could be where it is leaking also.

It's a head gasket, the pressure coming back from the compression is going to the overflow jug, seen it

Yep, head gasket is blown. If it is just at start up then you might have caught it early enough to save the engine. Get it to a Jaguar specialist ASAP.

Have an inexpensive *cooling system pressure test to see if you have an external or internal cooling system leak.

I have a jaguar 2.2d 98k. On colfstart the car blows out white smoke. The smoke smells sweet like antifreeze. But after a few minutes it stops.its a bit sluggish to drive until its heated. After warmed up It drives perfect with no overheating or no coolant loss. Oil looks fine aswell. I was thinking its the headgasket? What could it be?