[AccessD] Sorting combo based on Union query

I'm adding an "All" selection to a combo box using a union query more or less like this:

SELECT "All" as snoot from MyTable UNION SELECT MyTable.Field FROM MyTable;

MyTable.Field is defined as Text but contains Integer values.

Naturally the ascending sort order puts the numbers first. The "All" comes at the end of the list, and I want it at the top. I have tried adding an ORDER BY clause and by using DESC the "All" is at the top, but of course the numbers are then in reverse order. I have also swapped the order of the select statements but that makes no difference.

So, does anyone have a suggestion as to how I can get "All" at the top of the list with the rest of the list in numeric order?

Thanks,
Neal