Why am I getting a 404 server error htaccess rewrite rule? - .htaccess

Question

Im trying to add a simple rewrite rule so that any request sent to /api/v1/ will be processed by /api/v1/api.php
Currently it does a 404 on my when I try and run the example method /api/v1/example
Im following this tutorial but little confused where to put my rewrite rule in my current htaccess file.
What I have so far in my htaccess file is:
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
RewriteRule ^api/v1/(.*)$ api/v1/api.php?request=$1 [QSA,NC,L] # 404
</IfModule>
# END WordPress
Ive tried the wordpress method but that doesn't work either
add_rewrite_rule('^api/v1/(.*)$','api/v1/api.php?request=$1','top');
any help would be greatly appreciated.
Cheers :)

Answer 1

I'm doing similar - so in my /path/to/doc/root/api/v1/.htaccess I have
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /api/v1/index.php [L]
This ONLY catches requests in the /api/v1/ directory or lower, so the rest of my stuff still generates normal 404 errors, etc.