Referred to by police officers as Murder Squads or Murder Teams there are about 17 teams based at various police stations through out the MPS area - the details I have here relate to a team based at Belgravia nick (where 2 teams are based).
Each team is headed by a DCI
Under him/her are 3 DIs who split the individual cases between them as they come up.
Below them are 4-6 detective sergeants and below them, doing most of the work, are 20-25 DCs or PCs in plain clothes.
There are also civilian admin staff and data entry people.
A murder team is split into two uneven sections...
INSIDE INQUIRY TEAM consists of a senior DS (Case Manager) and a data entry team DCs, PCs and civillians) who are responsible for making sure all the information is inputed into the HOLMES 2 system - they are the only people who directly input data into HOLMES 2.
THE OUTSIDE INQUIRY TEAM consists of everyone else. In the first 36 hours of a job everyone will focus on that case as the leads start to dry up they return to the routine grind of wearing down their other cases. The Met's murder investigation policy is to run down every single fricking lead until either you catch the bastards responsible or run out of leads.
Most of the legwork is done by DCs who tool around London in unmarked cars usually bought second hand from other fleet providers. Murder squad cars don't carry lights, radios or sirens because it's not their job to rush about, the Met has people for that.
There's a briefing every morning so some things you see on TV are true.
The DCI, the DIs and the DSs sift through the information (using HOLMES) and assign ACTIONS which are given to DCs who go out and interview people, collect statements, evidence, track down family etc, this information is fed back to the Inside Inquiry Team who put it on HOLMES which generates more ACTIONS and so on and so forth.
It's sounds very bureaucratic but officers are expected to use their initiative, if an interview with one witness leads to another witness who's nearby the DC is expected to move on to that witness (he doesn't come back and wait to get another action). The big sin is not feeding this information back in a timely fashion and not letting your senior officer know what you're doing.
I hope that helps anyone doing murder related things in London - Present day.