His early career was as an economics journalist, working for The Times (1929–33), The Economist (1933–37) and the Daily Herald (1937–41), then as a civil servant in the Ministry of Supply and the Board of Trade.

[4] In his capacity as a journalist he was a senior figure in the XYZ Club, a clandestine organisation in the City of London dedicated to supplying Labour with financial intelligence.

[5] Alongside Evan Durbin and Hugh Gaitskell, he brought the thinking of John Maynard Keynes to the party, especially in relation to price determination.

Jay's politics during his period at the Board of Trade were characterised by a spirited fight for regional development and an aversion to currency devaluation, but it was his opposition to closer integration with Europe (see below) that led Harold Wilson to relieve him of his brief – a decision which Wilson, ever averse to conflict, explained was due to the need to have no ministers in the Cabinet over the age of 60.

[10] Jay was always fervently opposed to the UK's entry into the European Communities, and in 1970 was the first leading politician to argue that, because all three mainstream parties in Britain supported membership, only a national referendum of all electors could decide the matter in a fair manner.