1. Something then happened which did terrible damage to their relationship.

结构剖析：这是一个含有定语从句的复合句。主句是——Something then happened，从句是——which did terrible damage to their relationship。

它修饰先行词something，这个先行词是不定代词，引导英语从句的关系代词只能够用that，不能用which。由于something在句子中做宾语，所以就把这个引导词省略了。

此外，这个从句属于分隔式定语从句，因为它长于谓语，所以置于句尾，以平衡句子结构。

2. Dudley's wife, Amy, was found at the bottom of a staircase, dead from a broken neck.

结构剖析：这是一个简单句。主语是Dudley's wife，谓语是被动结构was found。

其余的成分，Amy是做主语Dulley’s wife的同位语，说明其名字，at the bottom of a staircase是介词短语做地点状语。最重要的是dead from a broken neck是做伴随状况状语。

3. .... it still cast a shadow over their relationship, just when they had become free to marry.

解析：when在这里不是连词，是副词，意思是“在这时候”，前面用了副词just来修饰副词when，加强语气，意思是“就在这时候”。

4. Officially he was, and though the queen always insisted that Dudley had been vindicated...

解析：he was是与后面的让步状语从句公用一个表语vindicated，这样显得表达更为简洁。