As notbob says, there will probably be an exclusion.
If there is an accident and you are at fault, then your ‘standard’ motor policy should cover you.
The ‘extra’ legal cover is there to fund claims brought by you for things such as injury or loss of earnings – essentially uninsured losses. However, as your insurers may look to pursue a subrogated claim to recover their outlay, and they can only do so in your name, then they *have* to include those losses in any claim they pursue, so it seems to me it’s rather an unnecessary expense.
However, as with all these things YMMV so RTFPolicy and decide.