When Oaktree Capital took over struggling luggage maker Tumi in 2002, one of the first things to ring alarm bells for Caleb Kramer was the handsome zips on the suitcases.

Kramer said: "We had a mess on our hands. The founder thought that you would know the difference between the zipper on one case and the other, that you would pick that case because the zipper had better performance characteristics. It was so over-engineered. We changed everything."