A1 Stamp at Border while Marriage Visa Still Valid

[vezlys]

Does anyone have an idea if the following will work. I’m an EEA citizen living in the UK, and recently married in the UK with a non-EEA citizen on a marriage visa. Our plan is to get the equivalent of the “EEA Family Permit” at the border in Calais, after a trip to Europe, which will be the “A1” or "EEA Dependant" stamp. This looks a valid way, after consulting this board and the official border guide.

The issue is that her marriage visa is still valid for a couple of months, so my worries is that they will claim that they don’t have to put the A1 stamp as she has a valid visa to enter the UK. Our immigration adviser said that you can’t re-enter the UK on a marriage visa once you’ve married, but I can’t find any official references to this. A marriage visa is a multiple entry visa, so I’ve not heard of any restrictions of this. If this would be the case, it would solve the problem, because then she wouldn’t have an existing valid visa anymore. Does anyone have any idea if this situation would work? Or might they only give the A1 stamp once the marriage visa has expired?

[vezlys]

To further clarify:

Is our immigration adviser correct in saying that, despite the marriage visa being a multiple entry visa valid for 6 months, it ceases to be valid once you've gotten married and you will no longer be able to enter the UK on it?

If this is not the case and it is still valid to enter on, will they refuse to put an A1/EEA Dependant stamp at the border? The problem with this is that our immigration adviser said that if my wife applies for a residence card while on a marriage visa, she would technically be doing so illegally since the marriage visa is no longer valid once married and you're actually supposed to leave the country once married and re-enter on another visa. We would obviously prefer to do it the legal way and apply once she has the A1/EEA Dependant stamp instead.