Illegal Tronc

My employer was illegally operating a Tronc over the past 8 years. It has been brought forth that operating a Tronc as he has been goes against some express terms within our contracts which specifically say that he can have no input over how tips are divided amongst the staff. This problem has been recently rectified and he is now facing some disciplinary action. However I have an enquiry as to what should have happened about the tax over the past 8 years.

Now normally if a Tronc is in use in a business in which tips are given then the Troncmaster is responsible for collection and payment of the tax. The employer is responsible for taking out National Insurance payments. Both of these deductions should be done before the money would reach our hands. 

However, within our contracts it states that we are responsible for our own tips and the taxes that are to be paid out on them. But this entire section of the contract was in breach due to the operation of the Tronc.

During the 8 years the Tronc was being operating illegally who was responsible for the payment of tax and National Insurance? Is it our employer, as he was operating a Tronc and in breach of our contracts, or was the responsibility still with us because of what was stated within our contracts despite this breach?