The reason that David Cameron uses the excuse of cost to resist the Finucane families call for an independent inquiry is because the De Silva report is about as far as the government thinks it can go.
Clearly the murder of Pat Finucane and others was sanctioned at a very high level of government. It is to establish at what just level that a full scale public inquiry is required.
What the De Silva report does provide is ample evidence of the need to keep the agencies and agents of the state under control. In Northern Ireland the whole security apparatus, including the legal system, became contaminated.
A similar thing is now happening in the remainder of the UK with proposals for secret courts and people being detained for years on end without trial. The hysteria aroused over Muslim clerics matches anything seen during the years of the Troubles in Northern Ireland. It is a sober reminder as to what happens when the lessons of history are not learned, namely that they simply get repeated leading to ever more innocent lives being wrecked.