Now at last Lib Dem ministers can say what they really think of their Tory bosses

The end is approaching for the Coalition's marriage of convenience

Norman Baker wrote to 43 constabularies

How do you serve under a Tory boss and yet convince your grassroots supporters you haven’t sold out your progressive principles?

At the same time how do you demonstrate that a coalition administration remains capable of running a competent government? And how do your tactics change as you prepare for the pre-election parting of the ways?

The conflicting pressures of the Coalition’s final year in office – described by one party source as “pragmatism vs principles” – are being agonised over at a senior level in the Liberal Democrats.

Such dilemmas constantly confront Lib Dem ministers Norman Baker at the Home Office and Simon Hughes at the Ministry of Justice (both on the left of their party) as they work alongside Tories Theresa May and Chris Grayling (both on the right of their party).

The pair were dispatched by Nick Clegg with the instruction to make the liberal voice heard more clearly in sensitive areas, from sentencing and immigration to human rights and civil liberties.

The appointments were a signal to Lib Dem activists that their values would be defended in office and that they would have a distinctive product to sell to voters appalled at the tie-up with Tories.

For Mr Baker it means trying to assert himself with a Secretary of State famed for her work ethic, attention to detail – and occasional reluctance to delegate. He has amassed a wide-ranging brief that brings in crime reduction, tackling violence against women, reducing animal experiments and gun licensing.

After an initial wariness, the pair have built a mutual respect and Mr Baker has achieved a higher profile than his predecessor, Jeremy Browne, who found himself isolated.

Mr Hughes has only been at the MoJ less than five months and has spoken of his determination to boost diversity in the legal profession and cut the number of women in prison.

The outside observer might imagine there is precious little meeting of minds with Chris Grayling. But the Tory Secretary of State’s hawkish language belies a strong commitment to rehabilitation shared with his Lib Dem minister.

In both departments, however, the Lib Dems are planning moves to get over the message of differentiation from the Conservatives more clearly.

Mr Baker is preparing to recommend a new approach to tackling drug abuse following a 15-month study of legislation around the world. It is certain to receive an immediate thumbs-down from Ms May – and its conclusions will head into next year’s Lib Dem manifesto.

The Lib Dems will also trumpet their success in knocking off the rough edges from Tory plans on immigration and their veto on moves to give the security services access to everyone’s online and email history.

At the MoJ, Mr Hughes is ready to react with horror to Mr Grayling’s proposals – due to become a Tory manifesto promise – to tear up the Human Rights Act.

The Lib Dem minister also has concerns about the potential impact of cuts to legal aid on access to justice. It would be no great surprise if his party campaigns next year on diluting the policy.

Messrs Baker and Hughes are likely to find themselves in different voting lobbies from Tory ministers next month when a Conservative MP’s call for automatic jail sentences for people twice caught carrying a knife is put to the Commons.

It will be a sign of things to come as the Coalition’s marriage of convenience comes to its inevitably scratchy divorce.