He hasn't shown his appreciation so he bought her flowers. (What...)
What happened was that he hadn't shown his appreciation so he bought her flowers.
You drove the car too fast. (What...)
What you did was drive the car too fast.
He understood the situation when he phoned. (It...)
It was when he phoned that he understood the situation.
The next thing he did was unbelievable. (What...)
What he did next was unbelievable.
They go to their local restaurant. (It...)
It is to their local restaurant they go.
Swimming is the best all round sport. (It...)
It is swimming that is the best all round sport.
We stayed in a five-star hotel. (The...)
The place where we stayed was a five-star hotel.
We should put his mattress on the bed. (What...)
What we should do is put his mattress on the bed.
I wanted some peace and quiet. (All...)
All I wanted was some peace and quiet.
He threw Frank out of the window. (It...)
It was Frank he threw out of the window.
I drank the Guinness. (What...)
What I did was drink the Guinness/What I drank was the Guinness.
His attitude annoyed me. (The...)
The thing that annoyed me was his attitude.