Complex sentence: When she died in 1992 she left her helmet and goggles to a fellow pilot named Alec Matthews, who in turn donated their joint memorabilia to the Thinktank Science Museum in Birmingham.
Split into simpler sentences: When she died in 1992 she left her helmet and goggles to a fellow pilot named Alec Matthews. He in turn donated their joint memorabilia to the Thinktank Science Museum in Birmingham.