I'm pleased they found the cause of Whirly's jam.
Thanks to those who added their experiences. It's good motivation for this student to continue to be paranoid about the pre-flight check.
I stopped at EGLK the other day in my car - to let my 3 year old get a fix of anoraking

- when I saw an AA5 land, taxi to the stand and a student and instructor get out. Several minutes later, another pilot got in, started and went straight to the power check area - followed by take-off, without ever having checked the outside of the aircraft. Now, if the CFI or his deputy (my instructor!) at my club saw me do that, I would not want to be on the receiving end of the one way conversation that would follow! (Which is, of course, why I fly from that club). Who knows what the previous flight/landing might have shaken loose?
Can anyone answer my question about using the trim tab on a PA28 following an elevator jam? Would it be necessary to maintain a higher approach speed to ensure trim tab authority?
Thanks
HH