Saying it was a private call and adding a sentimental to my mum doesn't make it any more right.......If there was something in your life so personal which meant you HAD to climb Silbury against all the signs asking you not to...then deciding it was the best time to make an important personal call from there....rather than quickly get down and get home to say it in person only smacks of self-justification to try to excuse your original boast, bearing in mind you claim that you made the phone call it wasn't someone phoning you and you answered them.
Strange how people will always have their phone with them no matter what the situation...but need to piss on monuments to see the carvings because they can't carry water(although 250ml bottles are easy to keep in a pocket).