The boss is asking the junior for a loan?
Nope not acceptable.
Most places I've worked this is against the rules anyway.
Quite honestly unless colleagues are VERY good friends outside of work borrowing from colleagues is usually a terrible idea
Where it's a boss asking an employee yes I'd consider that a major problem with the power dynamic and I would consider the boss inappropriate and unprofessional
but in this instance no they are not close friends outside of work
In that case absolutely not!
Bit off topic but this thread is a classic example of why grammar DOES matter!
You lend TO someone
You borrow FROM someone
If the manager forgets his wallet and asks to borrow some money for lunch or petrol I think that’s fine.
I disagree - if they're cognitively able enough to be a manager they can sort this kinda cock up out themselves! Either go hungry, make arrangements with family/friends NOT subordinates or find another solution.
At worst ask THEIR boss for a loan!
The subordinate will feel obligated to say yes unless they absolutely don't have the money on them and then they will feel guilty and awkward.
Even a half decent boss would NEVER put a subordinate in that position!
it’s been highlighted as a whistleblowing issue
That rather suggests this is tip of the iceberg!
This is not £10/£20. More like £100+ more than one occasion. manager approached subordinate
Wow! That sounds more like financial abuse/misconduct!
There's NO possible good reason to borrow those amounts!
Is the subordinate vulnerable in any other way?
This calls to mind a situation I became aware of one place I worked where one colleague kept borrowing money off another colleague, the lender had a learning disability and part of it was unusual generosity of spirit which the borrowing colleague was "testing" apparently  when it all came out borrowing colleague was sacked for financial misconduct and wasn't able to get another job for quite some time (quite rightly!)
@Horological "subordinate" still very much in use in civil service, military etc
Totally unacceptable op.
I sincerely hope it's not your job to discipline/manage such behaviour as you're coming here to ask, but then there seem to be rather a lot of managers who don't have the training or aptitude and come asking on mn.