I know this is a old classic one but i thought i might as well ask

Need to go to shanghai, found super cheap fares with KLM from London for 509$ and whilst i was searching i found fares with SAS from london connecting in CPH for 779$ which aint bad, here's the thing being based out of CPH, is there any chance in hell i can jump on board in CPH and skip the london flights and still pay for it?

Is it possible to check in for the london flight at CPH airport, and try and get boarding passes for the journey and then just skip the LON part?

(need to go wed/thur to mon/tue)