Illigal immigrant to marry uk based person

[mani]

its a problem that a friend is going thru

she's been seeing for a few years an illegal immigrant. she's born/bred in the uk and he isnt. hes from india.

would he have to go back to india - get married there and then apply for a visa or could they get married here and apply from here?

would it affect his chances of a marriage visa if he's already in the uk as an illegal even if he hands himself in to return to india?

i've always thought to be legally married in the uk he'd at least have to have a passport an EU one if nto a UK one...