I doubt it would be a problem, I think 9 times out of 10 though it depends who you get at MAN.
I worked there as a psa for 4 years and in that time it was hit and miss with who bothered with plastic bags/liquids etc. I even got a bottle of drink through once - full.
It was late at night and I was staff but still
And lets not forget a young boy got through
I think as long as you mention it first there shouldn't be a big to do about it.