Ummm the video doesnt even show where he/she is when it starts. And what is that stairs doing on the street? Movie is useless, sorry.
Here is a "legit" way of getting under SW however i take NO credit for this.
Start here in SW its like 100 yards away from the bank.
Then you jump on the torch, this will take a bit of time and you have to try and jump where it starts to incline.You should get bugged on the side of the torch.
Then jump on top of the torch and then on to the ledge.
Then just walk on the edge and you should fall down.
Then just use the video to get under the gates. So i guess you deserve some rep = ) Like I said I take NO credit for this.