Re: But I'm no actuarial expert !
"Most of the actuarial experts probably aren't good at facts and arithmetic either"
Actuaries are extremely good at processing facts and past statistics.
What they're not good at is working outside the lines they're not permitted to work outside (in the case of BT, allowing for changes in investment return rates and the looming probability of a large tranche of retirements that BT knew was coming where there wasn't 1:1 replacement (due to technology advances) as the IR actuaries were forced to assume.
I'm pretty sure that BT could have rearranged things so that the pension funds wouldn't have been seen as tax evasion, but IIRC the government was already gunning for them and it would have been easier to roll over and play dead. After all, the money was going out of the company either way so it didn't affect anyone's bonus at the time.