How do I prevent power saving?

Strangely enough, I have gone through bags of old camera equipment and found that I have the exact same flashgun. I have tested it today and there are no problems at all with it whatsoever, I upgraded to a Speedlite and have never used the Jessops flash since so it is as good as new even though I bought it second-hand. I don't actually recall any power-saving options, mine stays on until the batteries are flat.

