How to update the svn client version on Ubuntu 9.04

Recently, in our WSO2 Carbon code, we had to use svn externals to files. In older versions (before 1.6) of subversion, they supported externals only to folders. So after this, I had to update my subversion client version to 1.6.x to take a full update of Carbon code base. But my Ubuntu version is 9.04 and the latest subversion package it has is 1.5.4.

Then I searched for different options and found this post very useful. It is written for Ubuntu 8.10. But it works for any version of Ubuntu.