Horizontal Dropdown Menu in Twenty Eleven

Hi,

I wonder if someone could help me.

By default, Twenty Eleven will display a horizontal menu with a vertical drop down sub menu, i.e.

Home Services About Contact

If you have three pages under service, they will appear as a dropdown.

Services
This is one
This is two
This is three

What I want to achieve is to position the drop down sub pages side-by-side so that rather than a dropdown it appears like this:

Services
This is one This is two This is three

I was hoping this would be easy but I can’t find what to modify to make the LI’s appear beside each other just as they do for the primary menu.

I’d really appreciate it if someone could help.

Many thanks in advance,

Rob