It was a four flute normal carbide end mill, and not the ones designed for aluminium.

I have now tried the same but with a reduced depth of cut and reduced feed and it has done it well, albeit taking quite long.

Guys, I have a lot to learn regarding the optimum feeds and depth of cut, and lots of tests to do, I don't want to run before I can walk. But I thought I would post my first experience as I am sure many of you have been there too:)

Thank you for all the suggestions.