Your representative will negotiate an interim payment with the insurer of the at-fault driver. This is straightforward when there is no dispute, or no significant dispute, about who was responsible for causing the crash.
However, the insurers acting for the other driver will want to make their own enquires before admitting liability if liability is in the dispute or the case is potentially high value.
Because they do not wish to prejudice any potential criminal prosecution of the driver, it can be difficult to get liability evidence about the crash from the police.
It can take a long time for the case to be heard in the criminal courts if the other driver pleads not guilty to any criminal charge. This means that it can take months or close to a year to obtain evidence from the police.
However, insurers will usually want to provide financial support and rehabilitation when they realise that they are likely to ultimately be paying most (if not all) of a compensation claim.