Sounds like rod knock on acceleration & under load. See edit below as I did not expect to get many views.
*EDIT* This was rod knock, the engine was toast. It took me 3 weeks to get my £13,000 back after the dealership didn't have a leg to stand on. I caught it early as a lot of people may not have noticed it and thought it was normal engine sound, but I know my stuff to do with engines and cars. The car ended up getting another number plate and being sold on. I then got fines for parking 8 months later as the dealership never changed the registration over when I gave it back to them a few days later. I kept all the documentation etc and it was all thrown out. The dealership has now changed its name and still continues to trade......Make of that what you will. PLC and all that.
![](https://i.ytimg.com/vi/nBLf7KLCA_w/maxresdefault.jpg)