If I want to find the latest file (mtime) in a (big) directory containing subdirectories, how would I do it?

Lots of posts I've found suggest some variation of ls -lt | head (amusingly, many suggest ls -ltr | tail which is the same but less efficient) which is fine unless you have subdirectories (I do).

Then again, you could

find . -type f -exec ls -lt \{\} \+ | head

which will definitely do the trick for as many files as can be specified by one command, i.e. if you have a big directory, -exec...\+ will issue separate commands; therefore each group will be sorted by ls within itself but not over the total set; the head will therefore pick up the lastest entry of the first batch.

Any answers?