Help with .htaccess file to redirect to default language


I give up after some hours getting always the same.

I implemented what is shown in this article to get subdirectories for every language my website can be translated.

What I want now is to redirect urls not including a language to the url preceded with /en/, for example to

This is my .htaccess file using the line recommended everywhere and what I get for is

Options +FollowSymLinks

IndexIgnore */*

RewriteEngine on

RewriteRule !^(de|es|en)/ /en%{REQUEST_URI} [L,R=301]

# if a directory or a file exists, use it directly

RewriteCond %{REQUEST_FILENAME} !-f

RewriteCond %{REQUEST_FILENAME} !-d

# otherwise forward it to index.php

RewriteRule . index.php 

Any ideas?