The leader of Poland's main opposition party, Donald Tusk, is campaigning in the UK and the Irish Republic ahead of a election in Poland in October.
Donald Tusk is campaigning away from home
Three years after Poland's 2004 accession to the European Union, it is estimated that more than one million Poles now live in Britain.
Their votes could be crucial in what is expected to be a close general poll.
Prime Minister Jaroslaw Kaczynski, called the vote after his conservative coalition government collapsed.
Mr Tusk, who heads the pro-business Civic Platform (PO), has been canvassing in a supermarket in London, where he met Polish workers and picked out Polish products from the shelves.
Latest opinion polls indicate PO is running neck-and-neck with the Law and Justice Party (PiS), headed by Mr Kaczynski.
PM Jaroslaw Kaczynski (L) faces a tight contest
Every vote could prove vital, says the BBC's Neil Bowdler, and that is probably why he has taken time out of a hectic domestic campaign to spend a weekend in the UK and the Irish Republic.
Mr Tusk hopes many of them will use polling stations being set up in the two countries to cast their vote, and that many will vote for his brand of liberal pro-business politics.
In 2005 he lost both the presidential poll, to Lech Kaczynski, the prime minister's brother, and the parliamentary election to PiS.