"I'll be mother=I'll be the host" is this a common phrase for British people?
I heard this line from BBC TV Series Sherlock.
in the context, They seemed to mean the same thing, are they? and is it common with British people?

Question

"I'll be mother=I'll be the host"  is this a common phrase for British people?
I heard this line from BBC TV Series Sherlock. 
in the context, They seemed to mean the same thing, are they? and is it common with British people?

Answer

It's not very common at all! But yes, they mean the same thing - I'll be in charge/host.