Nickyboy, you have misunderstood the question.
Assume its a Garbo ??
I have had this same problem before, tried water, tapping, fingers, radiator and all manner of other suggestions.
Mine was stuck due to bits of Grit !!
The way I finally got the sections free was to use the half extension that fits up the 9 and 11m sections, place this inside the male end of the 13m section so it sits flush to the male end of the 11m section inside and tap it gently to force the 11m section free. You wont damage the half ex but you need to take care not to damage the 11m section, this was the only way I could free it but it worked with no damage to anything.