These are some very big cygnets. They look like they may be around 6 months of age. In that case, the parents will leave them alone for a while. If the parents are being chased by the other swans and if they think that the cygnets can survive on their own, they will leave the young to their own devices. It seems that the cygnets are staying together, which will also afford them more protection against predators and even the other swans. At 4-6 months of age, the parents have sufficiently taught them how to survive in their habitat. Unless you see an injury or the cygnets being chased so that they cannot get into the water or an area for safety, bathing, eating and drinking, we would leave them alone. However, if stress, ceasing of bathing, eating or being able to get in and out of the water safely, or injury, then we would suggest you contact the RSPCA. They will send someone out to assess the situation, and if necessary capture and relocate the cygnets to a safer habitat. The Regal Swan