In discussion with an ex-railway driver of many years experience I learned of a major safety concern, in the event that a guardless train should come off the rails.
If a train de-rails, the first thing the driver must do is run ahead to give a clear visible warning to an oncoming train that the track might not be clear. As can be seen whilst traveling, the clearance between trains passing on adjacent tracks is limited and any distortion to the natural line of the train, with carriages misaligned through having wheels off the track, poses a very serious danger of collision.
On a guardless train, with the driver running ahead to give warning, fearful and distressed passengers would be left alone and reliant solely on their own judgement. With no professional leadership or guidance they would most likely try to leave the stricken train, risking electrocution on the live rail, being mown down by fast approaching trains on multiple tracks, or suffering injuries whilst traversing difficult and unfamiliar territory. In a panic the injuries could be serious indeed.
The relationship between driver and guard is not simply differing jobs, which can be switched according to the will of the company. They are an integrated unit whose functions solidly interlink to maintain the safety of the train, its passengers and its crew. Take the guards off the trains and you have serious risks to health and safety. Clearly, Southern Rail managers have missed the point and do not understand how railways are supposed to operate. This alone is good enough reason to nationalise immediately and without compensation.
The RMT must be fully supported in its fight with the company as it puts passenger safety and rail workers jobs at risk. Rail strikes are rarely popular with commuters, but ultimately it is their overall safety which is at the heart of the matter. The union is fighting hard to preserve passenger safety, in the face of management whose only interest is profit.