The two discussed the detail of the timing of the announcement and their reactions to it. Mr Campbell even gave Lord Cranborne a copy of the response which Tony Blair was planning to make on Wednesday afternoon.
At their rendezvous on Monday, the two men agreed that Lord Cranborne would telephone the Conservative leader William Hague on Wednesday morning to tell him the deal had been struck.
The independent crossbench peers would then announce the compromise proposal at 3.15pm, Lord Cranborne would tell the Association of Conservative Peers at 3.30 pm and Mr Campbell would brief journalists at 3.45pm that the Prime Minister supported the deal.
The news that Lord Cranborne had a second rendezvous in Downing Street reveals the extent to which he was willing to collaborate with the Government to get the deal through. It will further infuriate the Tory leader, who is already angry that he was kept out of the picture until the arrangements were finalised.
Mr Hague fired Lord Cranborne after the peer clinched a deal with Mr Blair to allow about 100 hereditary peers to stay in the Lords until the upper chamber is fully reformed.
At the same time, the involvement of Mr Campbell, one of Tony Blair's most trusted advisers, in drawing up a presentational strategy also shows how worried the Government was about announcing the deal.
The Government confirmed last week that Lord Cranborne had met Mr Blair in Downing Street last Thursday to finalise details of the deal over a glass of whisky. In return, the Tories would agree not to wreck the legislation on hereditary peers or other Government Bills.
However, Downing Street has now confirmed that the second meeting between Lord Cranborne and the Prime Minister's advisers took place on Monday.
The news will shore up support for Mr Hague's decision to sack Lord Cranborne. However, the Tory leader is coming under increasing pressure from Conservatives in both the Commons and the Lords.
MPs on both the right and the left of the party are also privately discussing organising a vote of no confidence in Mr Hague. Although the leader's position is safe for now, they are drawing up plans to challenge him if the Tories' standing in the polls does not improve over the next few months.Reuse content