Knowing that your gates are 3.9m wide, and applying that as a scale to assess the task. It will depend very much on the length of the trailer and the width, don't forget that the actual length of the caravan is usually longer than the manufacturer's stated length becasue of the additional length of the A frame.
Most caravans are 7' 6" wide but in the last few years caravans have been allowed to be 8ft (2.4m). So fully understand the size of the caravan.
Road access from the top of your picture should be OK, but from the bottom, acuteness of the turn could be a problem for a car towing a caravan.
Doing a rough estimate the S bend from the gate to the level area at the front of the house looks to be about 20m. if this is 25% gradient then it is going to be a tough job to move a caravan up it. You will definitely need mechanical assistance. If you have a small caravan (short) I suspect you could tow the caravan up. I would suggest that you would be best served by an automatic transmission with fluid torque converter to avoid excessive clutch wear.
The other alternative which many have suggested is a caravan mover. Again you would have to look carefully at the specifications to ensure the model you choose is rated for your weight of caravan, and the working duty of a 25% gradient for 20m or so. I would strongly advise you write the details of your specific requirements on the order so it becomes a critical term in the contract with the supplier. You would need to uncouple (or couple when leaving for a holiday) the car and caravan at the bottom of the drive. You appear to have enough space to do so without causing a major obstruction to the road traffic for more than a few minuets.
Another factor to bear in mind is the battery needed to run the mover, and how it will be charged particularly on your homeward journey. You need to make sure it will be well charged when you get to the bottom of your drive, otherwise it might not have the charge to move the caravan all the way up your drive. This is a real concern, because many new cars have what is called a smart alternator, and they will not necessarily provide charge current to the caravan battery when the cars needs are satisfied. For this reason do ensure your towbar fitter is aware you need current for the caravan battery and fridge when towing. Some cars need a software change to ensure this is the case.
A lot to think about - Good luck