Complex sentence: Until 1997 Gordon was a Research Fellow at the University of Cambridge Computer Laboratory, after which he became joined the Microsoft Research laboratory in Cambridge, England, where he is a principal researcher in the Programming Principles and Tools group.
Split into simpler sentences: Until 1997 Gordon was a Research Fellow at the University of Cambridge Computer Laboratory. He then joined the Microsoft Research laboratory in Cambridge, England, where he is a principal researcher in the Programming Principles and Tools group.