Alex Salmond is expected to make his first appearance in the House of Commons since being elected as first minister for Scotland.
The MP for Banff and Buchan will take his Westminster seat after a 120-day absence, following the SNP's success in the Scottish election.
Mr Salmond hopes to speak on a debate on constitutional reforms, marking the debut parliamentary speech from a first minister.
While in London he will swear an oath to the Queen and become a privy councillor.
He will also meet with mayor of London Ken Livingstone in a fact-finding mission to seek ideas on ways to raise further funds for Scotland.
It is the first meeting between the two figures since the failed terrorist attack on Glasgow airport.
The SNP leader has been criticised for his failure to attend Commons debates, including specific sessions on Scottish issues.
Alistair Carmichael, the Liberal Democrats' Scotland spokesman, said last night: "I am delighted that, after finding time to visit Brussels and Northern Ireland, twice, Mr Salmond has at last been embarrassed into showing his face at Westminster."
Mr Salmond was also criticised for drawing both his MP and MSP salary and earlier this month was forced to set up a charitable fund into which he could channel his MSP salary.
The Mary Salmond Trust will receive around £18,000 a year to fund youth and community projects in north-east Scotland
Holyrood officials said Mr Salmond had to accept his £60,675 MP salary, plus a third of the £53,091 he receives for representing Gordon in the Scottish parliament.
The SNP leader plans to stand down from his Westminster seat at the next election to concentrate on the Scottish parliament, where is also paid £77,000 as first minister.
Mr Salmond's prolonged absence has not gone unnoticed by MPs and there were cries of "where is he" during today's prime minister's question time.
The Conservatives had hoped to expose the SNP-led Scottish parliament as a fault-line in Gordon Brown's leadership.
The prime minister has increasingly been asked how he justify passing policies on education and health that will have no impact on his own constituents in Kirkcaldy.
Mr Brown today played down Labour's defeat in the Scottish election and said he only hoped the SNP would not damage Scotland's economic prosperity.
He also called on David Cameron to make up his mind over devolution, noting his support for a Scottish parliament tends to increase north of the border.