Mr Cameron's objective is not so much a reformed EU, as a deformed one - in the sense of being disabled, handicapped, not fully functional. As was forecast, the Union that is envisaged in the proposals for an EU-UK settlement is a two-tier union.

An embryonic two-tier EU has existed for some time, particularly since the creation of the euro, but under this proposal it is likely to move from an ad hoc arrangement to a permanent system in which there will be a clear division of states into two classes of membership.

In that sense Mr Cameron appears to be achieving his goal, though he will have difficulty convincing the euro-sceptics in his own party of that, never mind the out and out (in every sense) Little Englanders of UKIP.

As Mr Tusk bluntly states in the first sentence of his proposal, the EU's key objective had to be, and is, preserving the unity of the Union, which in this context means keeping the UK in. A UK departure would do more harm to the whole European project than conceding the two-tier principle.

Mr Cameron may be beginning to regret some of the language he used in first formulating his demands. On the 'ever closer union' it seems that he is being offered a little sugar to enable him to swallow it -a written reassurance that, as everyone always knew, this was never more than a pious aspiration, never an explicit commitment to a European federation or super-state. There is no offer to delete the phrase from the Treaties.

The two tiers are most obvious in the section on the euro zone, with the EU being, understandably, more concerned with ensuring that progress towards full economic and monetary union will not be impeded, than it is about guaranteeing that those in Division Two will not be put at any disadvantage.

On Competitiveness - making the EU more efficient in Mr Cameron's lexicon - the draft deal adds nothing to already stated positions on the importance of the internal market, and the need to reduce administrative burdens on business while, at the same time, 'continuing to ensure high regulatory standards', all based, of course, on regulation at European level.

The section on migrants and welfare benefits is the meat in Mr Tusk's sandwich. There is a worthy effort here to balance free movement against the real problem caused by the increased flow of migrants and the soaring costs of social welfare on member states' budgets. The approach is a well-tried EU one - preserve the principle but ease the problem via temporary concessions in exceptional circumstances.

This is not exactly what Mr Cameron was asking for, but neither is it a flat rebuttal. Tying the level of in-work benefits for migrants paid to dependants in their country of origin, to the (much-lower) costs of living in those countries will be denounced as discrimination but has a smack of common sense about it. Just the sort of thing Mr Cameron will need to bolster his claim that he has not come home entirely empty-handed.

The fourth item on the Tusk agenda is a real dog's dinner. Mr Cameron has been given an appropriately opaque fig-leaf on the issue of the sovereignty of national parliaments and his demand that there should be a mechanism to allow them, or a combination of them, a veto on proposals for new European legislation..

This could be either a complicated mechanism that will mean little and rarely if ever be used, or it just could be another spanner in the works of an already cumbersome machine. It is patently unnecessary, as member states, directly or through their contacts in and with the European Commission and through expert working parties and other groups, have ample opportunity to mount strong opposition to any proposal at the earliest stages. Besides which there is the European Parliament, made up of MEPs who are also members of the same parties that sit in national parliaments, but who have far more time and expertise to scrutinise European legislative proposals..

It is ironic that Mr Cameron poses as the great defender of the sovereignty of the national Parliament vis a vis Europe just when he has handed over its sovereignty to the lottery of a referendum, a device with no place in British constitutional practice.

For all this the Tusk proposal may be just enough to allow Mr Cameron to win his referendum and keep Britain, in without too much concession of principle by the EU. But a formalised two-tier Europe will be a weaker Europe, and not one that should be welcomed in Ireland, north or south.

It could all go wrong. The British media are, for the most part, rampantly euro-sceptic, as are large sections of the British public. People who play with fire often get burnt, and in turning to a referendum Mr Cameron is playing with fire.