Sarah Wollaston is no fan of David Cameron - that's why her EU defection matters

A few months ago, the Tory MP Sarah Wollaston dismissed David Cameron's renegotiation deal with the EU as 'threadbare'.

She told colleagues in the Commons that it would do nothing to reduce the numbers of migrants coming to Britain and subsequently decided to join the Leave campaign and vote for Brexit.

Today, the GP and the chair of the Commons Health Committee announced she was defecting.

No one could accuse Dr Wollaston of being a puppet.

She was selected as the 2010 Conservative candidate in her Devon seat in a local primary.

At the time, primaries (where local people chose the party's candidate before the election) was David Cameron's big idea after the expenses scandal (the previous MP in her Totnes seat was the one who said his house looked a bit like 'Balmoral').

Since then, Mr Cameron could have been forgiven for questioning his big primaries idea.

The independently minded MP has complained how she is told how to vote by party whips, she has rebelled, criticised government policy and spoken about the privileged backgrounds of the Tory leadership.

David Cameron will forget all that with a single mouthful of his cornflakes this morning as Dr Wollaston denounced the Vote Leave campaign and said she'll be voting to stay in the EU.

Her reason? The NHS.

More specifically, the claims by the Leave campaign that some of the '£350 million per week' we spend on the EU could be spent on the Health Service.

The £350 million claim has been much criticised as it does not include the UK rebate nor the money the EU spends in the UK on fishing, agriculture and deprived areas.

And now, it seems that is the main reason for Dr Wollaston's decision to switch sides.

The Leave campaign has question her sudden conversion and called her decision 'bizarre'.

But they must worry - just as the Remain campaign must hope - that this defection could encourage one or two other Tories to do the same.