I'm taking up Running because the job I am applying for I have to be able to run 1.5km and I would like advice on the best way to start to build up my running because from what I remember it was dreadful at school. I do other activities so i'm quite fit.

Hi!
Congrats on starting to run....its a great feeling to just be out running alone with the road. The single most important thing is to have a good pair of shoes...this will make the difference between enjoying and hating running. SPEND THE MONEY to get a proper shoe fitting at a specialty store...even the most expensive pair of shoes can hurt or hinder a runner if they don't work for your body.
Start slow and short and work up to higher distances...run every other day and cross train with whatever other sports you do on your off days. Try keeping a running diary of the time, distance, pace, route, shoes, temperature of each run so you can see what works for you.
I started out not running at all and completed a half marathon 3 months later...I'm running a full marathon in January. You can definitely make it happen and enjoy it too!
Good luck!