Prime Minister John Key’s unusual first week in the job will continue in London overnight where he will meet the Queen, British Prime Minister Gordon Brown and his half brother for the first time.

Key left the Apec meeting in Peru yesterday for a 24 hour trip to Britain.

Just before he visits Buckingham Palace and 10 Downing Street, Mr Key will take a more personal journey and meet his older half-brother Martyn Key.

The 68-year-old is one of two sons from an earlier marriage of John Key’s father, George. The other lives in Canada.

The New Zealand Herald found Martyn Key when it looked into John Key’s background and discovered the relationship.

There had been no contact between the two branches of the Key family for more than 30 years prior to that and since the discovery the pair have exchanged emails.

After the family meeting, Key and Brown are expected to discuss the international financial crisis and the prospect of global economic recession.

The meeting comes a day after Brown and Chancellor of the Exchequer Alistair Darling are expected to unveil a stimulus package that will cut sales tax from 17.5 per cent to 15 per cent.

Other moves include slapping a tiered tax on those flying out of Britain with those travelling to New Zealand hit the hardest.

The move could be a blow to the New Zealand tourism industry, which Key — who is also Tourism Minister — would be keen to soften.

Other issues likely to be discussed are New Zealand’s commitment to the war in Afghanistan and trade.

Key will also meet Conservative Party leader David Cameron and London Mayor Boris Johnson, who will attend the launch of the giant promotional rugby ball for the Rugby World Cup in 2011 near the Tower of London.

Key left New Zealand for the Apec meeting after being sworn in last Wednesday and arrives back on Thursday afternoon to prepare for the opening of Parliament on December 8.