He admits he's been spending most of his time on it recently, organising amendments, building coalitions and fielding inquiries. "But in a funny way I have a feeling that my hour has come," he says.
"Having spent all this time deeply enmeshed in this amazing and wonderful sector, I can now take part in what is certainly a major piece of legislation, which will affect the sector for ever more."
Thirty-plus years as a specialist charity lawyer have underpinned his contributions to the hearings of the joint parliamentary committee that scrutinised the draft Bill last summer and the 20 or so hours of debate in the Lords so far. His tour de force came last month, when he unpicked the case of re Resch's Will Trusts, a Privy Council judgement of 1967 that has led to uncertainty about whether the Bill will result in recalcitrant fee-paying schools being obliged to provide real public benefit to justify their charitable status in future.
It was a complex exposition, but Phillips spent 25 years as the 'legal eagle' on Radio 2's Jimmy Young Show and prides himself on making the law comprehensible to the ordinary person, so he rounded it off with a memorable sound bite.
"What I have endeavoured to do today - and I am sorry I have spent so much time doing it - is to demonstrate that re Resch is a blancmange," he told the Grand Committee. " It is a foundation for nothing but a sinking feeling."
The Government has so far refused to accept the amendment that he thinks would settle the uncertainty, even though it has been supported by much of the voluntary sector and has had discreet encouragement from within the Charity Commission.
That refusal fills Phillips with exasperation, because he thinks that, without the amendment, "the laggards in the independent sector who are doing little or nothing in terms of making their benefits more widely available might well be able, bluntly, to give two fingers to the Charity Commission".
He thinks the Government's refusal to move is "pure politics", and accuses ministers of running scared of right-wing newspapers that might be prompted by the private school lobby to attack it as the election approaches.
The latest development, of course, is that further Lords committee hearings have been postponed and it is now almost impossible that there will be enough parliamentary time to get the Bill into law before the election, widely expected on 5 May. This would mean that Phillips and others would have to gear themselves up to do it all again if the Bill is reintroduced.
"The thought of going through this route march a second time does not fill me with joy," he says.
A Liberal Democrat, he describes himself as "a bloody-minded, independent Whig", a political term first used in the 17th century for those upholding popular rights and opposing the King. He was briefly Labour candidate for North Norfolk, but was expelled from the party for writing to The Times deploring its policy at the time of nationalising the top 100 companies and indemnifying trade unionists with criminal convictions.
"I was excommunicated," he says. "It was painful because it halted my parliamentary ambitions. With hindsight, though, I've no regrets.
"I've been in the Lords in a golden period, I fought four elections for the Liberals and had a wonderful life in the law, setting up my own firm. I am a lawyer first and foremost."