Shower Cable Size

I am installing a new shower in my bathroom.
I have to run new cable about 8 - 10m to a 10.5KW shower. Through observing this website and talking to an electrician it seems a 10mm cable and 45A protection will be sufficient yet another website states that 16mm cable and a 50A protector are needed. The website concerned is diydoctor at http://www.diydoctor.org.uk/projects/electricshower.htm
I have already bought the 10mm cable and was about to install it.
Will it be OK ?
Stuart

It will be fine, unless the cable is grouped with others or excessivly insulated along its route such that overheating is a risk -use the cable calculator herehttp://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html to see the effect of changing these things.