Cameron rang Kenny the evening before he gave his speech in which he said his Conservative party were planning on providing UK voters with an "in or out" referendum on EU membership should they win the next General Election.
Cameron said he would renegotiate terms on Britain's membership -- and then put a referendum to the British people. If his party wins the next General Election in two years time, it will be approximately 2016 before a referendum is put to the electorate.
However, were Britain to pull away from the EU, it would cause Ireland some difficulty, especially if it's to move towards long-term prosperity.
During Cameron's 15- minute phone call to Mr Kenny on Tuesday evening, the Taoiseach listened intently as the British Prime Minister gave him advance notice of his speech that outlined a scenario which could result in Ireland's biggest trading partner exiting the EU.
The words will have made Mr Kenny decidedly uneasy as Ireland begins to prepare for the economic uncertainty triggered by Mr Cameron's decision to hold a referendum on Britain's membership of the EU before 2017. The implications of a departure of Britain would be significant for Ireland, with a fundamental change in our trading relationship with the UK.