I can't quite remember when it was that you started doing th

I can't quite remember when it was that you started doing the work.麻烦讲一下句子的结构吧.
it is ...that是强调句型,在这里倒装吗?麻烦详细讲一下句子结构吧.可以的话希望多举几个例子,谢谢啦,鞠躬~~~