Can anyone tell me please - why does everyone refer to the National Health Service as being FREE?

We pay our National Insurance contributions as did our fathers before us and their fathers this pays for the national health service - so why do particularly politicians refer to it as FREE? i admit that we don't pay the doctor when we visit him, nor do we pay the surgeon who carries out our operation, instead we are paying regular installments into the nation health insurance which covers us for health problems so it is not FREE - we are continually paying for this service throughout our lives from the age of 16 to retirement age - how is this FREE? I don't begrudge paying this insurance so that when i need it the service is there but i do object to the reference 'FREE' ? WHAT ARE YOUR THOUGHTS?