Leading article: Mr Mugabe must not be a fatal distraction

Seen through a British prism, the European UnionAfrican Union summit, which opens in Lisbon tomorrow, has two distinct aspects. The first is the fraught bilateral relationship between Britain and Zimbabwe. The second is all the rest of the summit's business. The question is: how far one will overshadow the other?

We have known for some time that the Prime Minister intended to boycott the summit if the President of Zimbabwe was attending. He cannot be criticised for keeping his word. Nor can Britain be taken to task for the situation that has arisen. This is primarily the responsibility of Portugal, which holds the EU presidency. It took the reprehensible decision to invite Robert Mugabe, apparently in the name of inclusivity. In so doing, it violated the EU's own travel ban on leading members of the Zimbabwe government. And, while a more sophisticated politician might have found a pretext not to travel to Lisbon, the President of Zimbabwe never lets slip a chance to tweak the tail of the British.

Had the summit gone ahead without a British presence, this would have been unfortunate, not least because of the priority both Mr Brown and his predecessor, Tony Blair, have given to promoting African issues internationally. But it would have had the virtue of clarity. It now transpires, however, that Mr Brown's boycott will not be quite all it seemed. While Britain will not be represented in Lisbon at head of government level, it will be represented. Baroness Amos, a former cabinet minister and senior Labour figure, will be attending.

It is true that she is not in the Government, having departed at the reshuffle that followed Mr Brown's arrival at No 10, but she is a senior figure, and when she left the Cabinet it was to become Britain's nominee for the new post of the EU's special envoy to the African Union. As such her appointment has not been the foregone conclusion some believed it is clearly in her, and Britain's, interests to be in Lisbon. Her attendance, however, severely dilutes Mr Brown's message.

Baroness Amos has said that she will use her presence to make Mr Mugabe aware in no uncertain terms of Britain's views about his leadership and we hope she does. The risk, however, is that the continuing war of attrition between London and Harare will divert attention from the much larger project: the growth of a mutually beneficial and highly productive relationship between the EU and the African Union.

One of the EU's longstanding defects is that it underestimates the international influence it can exert when it acts cohesively. That the OAU renamed itself the African Union was a tribute to the EU as a model for regional organisations. And the colonial legacies which tend to divide EU countries and fuel resentment in some parts of Africa can also be a strength. There is extensive knowledge and experience on both sides that could be put to much better use.

Central to the EU-AU summit will be a review of the two-year-old EU-Africa Joint Strategy, which covers predictable areas such as financial assistance, trade, governance and human rights. The picture in all these areas is more mixed and, in many places, more hopeful than the hackneyed image of Africa as a basket-case would suggest. And there is much more that the EU could do, in the way of opening its markets to African exports, fostering Africa's peace-keeping operations and supporting progress towards democracy.

This discussion would probably have been more productive if Robert Mugabe were not contributing his distracting presence. Now that he is, we can only hope that he will be able to learn something about the benefits of co-operation and what goes into making countries prosperous and content.