Help! Fillet of beef cooking time

[MarmMummy]

I've left it rather to the last minute but was planning to cook a good sized fillet of beef tomorrow.
I can't find my original recipe but recall I rubbed it with horseradish wrapped it in Parma ham and roasted it for about 40 mins for rare.

Does that sound about right?!

It will be enough beef to feed 10.

About right - depends on how big it is - usually for beef would be 15mins/lb for rare plus 15mins extra, 20-25 for medium then30 for well done.

Thanks!!