Gordon Brown will strive to put his domestic problems behind him when he embarks tomorrow on a 30,000-mile epic journey that he hopes will portray him as a statesman, world diplomat and defender of British interests.

For much of the next three weeks, as his party battles it out with the SNP in another critical by-election, the Prime Minister will be out of the country attending summits, visiting trouble spots and representing Britain at the Olympic Games.

People around Mr Brown expected him to do far less travelling than Tony Blair, who clearly enjoyed strutting the world stage. Now it has become part of Mr Brown’s survival kit, as he goes from one capital to another, urging oil producers to increase their output, seeking help for developing countries that face a food crisis and coordinating international action to combat the credit crunch.

Mr Brown’s strategists believe that he has to make the most of what have been seen up to now as his disadvantages; his seriousness, dourness even, can become an asset as he bargains for Britain at the international table.

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They want to draw a contrast between Mr Brown the substantial politician and David Cameron the flashy public relations man. Only two weekends ago he made a 6,000-mile round trip to Jedda, Saudi Arabia, to spend only a few hours on the ground discussing oil prices.

But veterans of foreign travel with prime ministers know that such trips rarely go to plan; media minders find that domestic troubles have a habit of intruding when their boss wants to concentrate on world affairs. Ask John Major, whose problems with his Euro-sceptics perpetually haunted him overseas. Ask Tony Blair, who was told during a trip to the Far East of the death of the government weapons expert David Kelly.

Even if Mr Brown had wanted to break the convention that prime ministers do not campaign in by-elections, he would have had little time to spend in Glasgow East before its electorate votes to determine the tone of his summer on July 24.

Tomorrow Mr Brown will climb aboard a private charter aircraft to take him the 5,500 miles to Hokkaido, in northern Japan, for his first G8 summit. He will be there until Thursday talking about the energy and food crises, Zimbabwe, climate change, and holding his first head-to-head meeting with President Medvedev of Russia.

He will miss his weekly duel with Mr Cameron on Wednesday. Harriet Harman will fill the breach as Mr Brown, several time zones ahead, sits down to dinner with the leaders of the world’s richest countries, alongside those from China, India, Brazil, South Africa and Mexico.

The Prime Minister will then be popping over to Paris for an informal get-together – grandly entitled the Mediterranean summit – with EU leaders and others as the current EU president, Nicolas Sarkozy, presses his idea of a Union involving the countries of northern Africa.

Mr Brown will be back in time for his last Prime Minister’s questions of the summer before heading off again the following weekend, July 20 and 21, to the Middle East for a 6,000-mile, 20-hour round trip during which he will hold talks with leaders from across the region.

Then he will face the chill reality of British politics again. Glasgow East votes the following Thursday. A win for Mr Brown, however slender, will ease his pain. A victory for the SNP will give him more than a headache.

Either way, Mr Brown will have one of the most important speeches of his life on July 25 when he addresses Labour’s National Policy Forum in Warwick. What he says will be shaped by what has happened in Glasgow. A reverse means that Mr Brown will once again be out to kill the impression that he is on his way out as talk of challenges against him, or even a voluntary departure, resurface. A success will put the focus on how Mr Brown can respond to union demands for more rights in a Warwick II agreement.

After all that Mr Brown will go on holiday – somewhere in Britain, according to friends – before travelling to Beijing (another 10,000 miles there and back) for the last few days of competition and the closing ceremony, as the Chinese capital hands over to London for the 2012 Games.

On all those trips Mr Brown will be hoping, almost certainly in vain, that things stay quiet on the home front.

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