Luke was convicted by a majority decision which suggests that the circumstantial evidence wasn’t as strong as you suggest.
As to moving Luke’s case forward, Stephen Downing was in prison for 27 years after two appeals were turned down. The jury found him guilty by a unanimous verdict. He wasn’t even considered for parole. His conviction was unsafe.
Not a good example. After a long and extensive re-investigation following his release -
“After failing to link any other person with the murder, and unable to eliminate Downing as the suspect, the police declared the case closed and said they were not looking for anyone else.[16] Even though Downing remained the prime suspect, under the "double jeopardy" rules in place at the time a suspect could not be re-arrested and charged with a crime they had previously been acquitted of.[4] The police said that, had the law been different, they would have applied to the Crown Prosecution Service (CPS) to again charge Downing with the murder.[4] The findings of the investigation led to public doubts over whether he should have been released.[5]”