What was the first face to face meeting between Xavier and Sinister?

[jignat]

Sinister debuted when Chuck was in Shiar space in the 200's of Uncanny vol.1

Skimming vol. 2 Nicieza/Lobdell issues, Sinister appeared in X-cutioner's song but Chuck was unconscious. He tussled with some X-men here and there in the 20's , but I can't recall when he first interacted with Chuck on panel.

Thanks for any help.

[dragon1440]

As part of the Black Womb project, Sinster under the name of Dr. Nathan Milbury, experimented on Charles as a kid.