Relative Clause Type #3: Preposition + Whom/Which

In some cases, a relative clause will have a preposition at the end. Prepositions are the small words that we normally see before places in space and time:

• at work
• after lunch

It’s not a problem for a relative clause to end with a preposition, but many writers aren’t comfortable leaving it there because a preposition is literally a word that goes BEFORE a place.

• pre = before
• position = place

Today, not many people pay attention to this, but it often improves clarity to move the preposition in front of the relative pronoun at the start of the relative clause. Try both version and trust your ears.

Here are a few typical examples:

1. That’s the table which I left my bag under.

The relative clause ends with a preposition. We can move the preposition in front of the relative pronoun:

• That’s the table under which I left my bag.

2. Frank is the guy whom you should give the file to.

• Frank is the guy to whom you should give the file.

3. That’s the lady whom you need to send the package to.

• That’s the lady to whom you need to send the package.

Expressions: Preposition Phrase + Which/Whom

thanks to which

I'd like to thank our wonderful president for her leadership. Thanks to her leadership, we were able to exceed all of our targets.

• I'd like to thank our wonderful president for her leadership, thanks to which we were able to exceed all of our targets.

thanks to whom (singular & plural)

I'd like to thank John. Thanks to him, we were able to finish this project on time.

• I'd like to thank John, thanks to whom we were able to finish this project on time.

I’m grateful for the help provided by everyone in John’s department. Thanks to them, we were able to locate the records more quickly.

• I’m grateful for the help provided by everyone in John’s department, thanks to whom we were able to locate the records more quickly.

due to which 

There’s been a big change in the market. Due to this change, we can no longer do things the same way.

• There’s been a big change in the market, due to which we can no longer do things the same way.

as a result of which 

This is the problem. As a result of this problem, our project will be delayed.

• This is the problem, as a result of which our project will be delayed.

according to whom 

The police spoke with the witness. According to him, the robbers escaped in a helicopter.

The police spoke with the witness, according to whom the robbers escaped in a helicopter.