Do you own the land along the proposed path of the cable? If so it is up to you.
Otherwise you would need to contact whoever owns it (or council if theirs) and get written permission to do so, but I am not a solicitor so if in doubt get professional advice.
As far as the cable itself is concerned, you might want to put in duct and then you can pull through other/replacement cables in the future without any more digging. On private land there is no specific depth requirement other than it should be deep enough not to be damaged, so around 0.5m is usually plenty. But if it crosses arable land it should be something like 1-1.2m deep to avoid damage if ploughed, etc, and the power companies have guidance for cables for footpaths and main highways, etc.