A pal applied for a secondment within her organisation to a different team. She succeeded but her team manager refused to keep her job open for her*. Things changed and she has now been offered the job as permanent role (and accepted it).
She was been told she had to resign from her existing role, possibly because of *, and has done so, but that's probably moot, given the new role is now permanent?
Would have the insistence to resign/resignation itself have been lawful/effective in the original circumstances?
depends on the contract and the terms of the secondment. A true secondment is a temporary internal transfer and the original job would be held open but as ever it depends on the actual circumstances.
Existing role or from the company?
Never heard of having to resign to transfer within an organisation.
I worked in a large plc with many different legal entities and operating businesses, sometime an internal transfer from one to another required a resignation/re-employment but continuation of employment from a pension and benefits perspective - is a bit of a surprise when you get a P45 in the post!