Don't be so sure the RSPCA will do much, if my experience is anything to go by.
While living down in Wales a few years ago we had two instances of poor dog ownership by neighbours.
The first was a family who's property abutted on the bottom of ours. He had two ruddy great German Shepards but they were either kept outside in the garden or in a shed, not allowed in the house so far as we could tell. They got exercised about once a week which consisted of this guy running them, off the lead, around the block a couple of times. Someone (not us) must have called the RSPCA as we were actually "live" when they turned up and overheard the conversation in the back garden. Basically he spun them a yarn which they must have swallowed, as nothing happened and the situation went back to previous. Eventually they moved.
Case No.2. Our immediate next door neighbour a(single mother with three kids) cquired a small dog. Kicked out in the back garden, constantly yapping and barking (not much fun when working nights). No effort to control or train it. These people also had a cat and the final straw came when we saw the dog grab the cat in its mouth and start shaking it. My missus banged on the window and shouted "oi", which caused the dog to drop the cat which then escaped. At that point I wrote a letter to the RSPCA describing what I'd seen and expressing concern for the welfare of the child, should the dog decide to worry them rather than the cat. And, guess what - nothing happened. Weeks went by, dog still there, no sign of the RSPCA or anyone else turning up to investigate the situation. It was only a few months later they must have got rid of the dog themselves as it all went quiet and wasn't there anymore.
The other thing to bear in mind with the RSPCA, is that if they do take the dog off the person they have a bit of a reputation for putting down pets they can't rehome. So you could inadvertently be signing the animal's death warrant.
While living down in Wales a few years ago we had two instances of poor dog ownership by neighbours.
The first was a family who's property abutted on the bottom of ours. He had two ruddy great German Shepards but they were either kept outside in the garden or in a shed, not allowed in the house so far as we could tell. They got exercised about once a week which consisted of this guy running them, off the lead, around the block a couple of times. Someone (not us) must have called the RSPCA as we were actually "live" when they turned up and overheard the conversation in the back garden. Basically he spun them a yarn which they must have swallowed, as nothing happened and the situation went back to previous. Eventually they moved.
Case No.2. Our immediate next door neighbour a(single mother with three kids) cquired a small dog. Kicked out in the back garden, constantly yapping and barking (not much fun when working nights). No effort to control or train it. These people also had a cat and the final straw came when we saw the dog grab the cat in its mouth and start shaking it. My missus banged on the window and shouted "oi", which caused the dog to drop the cat which then escaped. At that point I wrote a letter to the RSPCA describing what I'd seen and expressing concern for the welfare of the child, should the dog decide to worry them rather than the cat. And, guess what - nothing happened. Weeks went by, dog still there, no sign of the RSPCA or anyone else turning up to investigate the situation. It was only a few months later they must have got rid of the dog themselves as it all went quiet and wasn't there anymore.
The other thing to bear in mind with the RSPCA, is that if they do take the dog off the person they have a bit of a reputation for putting down pets they can't rehome. So you could inadvertently be signing the animal's death warrant.