It's all a little bit more complicated than it might first appear though isn't it?
With many crime there are little or no leads - or leads peter out pretty quickly. Even if a suspect is caught on CCTV often images are so grainy then they can be of little or no use: even if a clear image is caught then it all relys on someone recognising them.... images are regularly circulated internally and externally but if no-one recognises them then your options are drying up fast.
Descriptions are all very well - and victims/witnesses may be invited to look at "mug shots". However, the process is goverened by the Law (and of course, the police have to follow it). This has to include putting in "duff" images (even ones that clearly couldn't be the suspecy) and if you describe, say, the suspect as having a big scar down the left side of his face then you have to pixelate out the left hand side of all of the images' faces. (!)
The problem is most people give descriptions that are so vague, not through their own fault, that they are next to useless: unless the description includes clothing - and police are on scene pretty quickly - then it's an uphill struggle.
What about forensics? The things that prints can be lifted off is still pretty limited, criminals also wear gloves, DNA is pretty fragile. It isn't all CSI Miami unfortunately.
Then there is the question of resources. Does anyone have any idea, even roughly, of how many officers are available to take calls at any one time? Or how many cases officers in the burglary/robbery/whatever squad have to deal with at any one time?
The clear-up rate for burglaries and knife-crime hover around the 25% mark in the Met I believe.... which, all things considered, isn't bad.
Another issue is that the police seem to bear the brunt of criticisms levelled at the criminal justice system as a whole - a fair amount of criticism needs to be directed at other areas: The CPS, the courts and so on. The police are doing their job: Lewisham Custody Suite is regularly full to the brim (literally) with robbers, burglars and violent criminals, many of them have a history going back years, they are being put before the courts and so on.....which is what the police exist to do.
The one things I do concede that The Met are terrible at is in communicating with people: on a PR level, in managing expectations and in keeping people up to date and informed.
Despite all that there has been no news at all from the police. Is this going to be another unsolved crime put on crimewatch months after it occurred.
Oh, I didn't realise the police did a daily/weekly update to the general population as to whether people have, or have not, been arrested/charged with specific crimes? Were you expecting a big poster outside the Job Centre with an announcement "another case cracked!"