GISELA Stuart looked unusually flustered as she raced into the main lobby of the House of Commons yesterday. The little-known Labour MP for Edgbaston was much in demand.

Within hours Tony Blair could have signed up to a European constitution that she and 12 wise men helped to draft.

But it was not the finer points of legislative detail that had thrown her off balance.

The German-born MP, elected to an English constituency, who has been diligently representing British interests in Brussels, had spent the previous evening writing two essays that had just been completely erased from her computer.

She rolled her eyes in mild exasperation as she scanned the room for somewhere to sit. ''I just need to put on a bit of slap (makeup) because I'm doing television at 9.30am,'' she whispered as we perched at a table in one of the grander House of Commons' lobbies.

It wasn't that Ms Stuart was being grandiose - rather that despite her already packed schedule she was doing her best to squeeze in one more commitment.

The softly-spoken MP describes herself as ''German by birth and British by choice'' and has earned a reputation as a sane and authoritative voice on the workings of Europe.

So after 16 months spent in all-night sittings, living out of a suitcase, shuttling between Brussels and Birmingham, Prague and the Baltic states, Ms Stuart explained why a European constitution was so important and where the major battlegrounds would be this weekend.

''If you want the union to go on being successful, as it was for me and for my kids' generation, then the whole way the union organises itself has to change to make way for enlargement,'' she said. ''Because what you can do with six countries, you can't do with 25. Things as simple as heads of government sitting round a table and everyone does a five-minute spiel. With six countries that takes half an hour, with 25 you'll be there all day.''

The heads of government are meeting in Brussels this weekend to decide whether to sign up or whether further changes are needed.

''There are three elements to this,'' Ms Stuart said. ''First, it will bring all previous treaties together so even a school child can go and pick up one document containing all the rules of the European Union. Now, it's still a pretty hefty document, but at least it is all in one book.

''Secondly, it makes some of the procedures simpler and changes the language, so instead of thousands of different rules and regulations, they are actual laws and everybody can understand them. These are two things I hope the heads of government will take on board.

''Then there are bits in there that are deeply political - should we really create a European public prosecutor? Do we need a European Union foreign minister?

''And because it's so important, I think, I hope the government will only say yes to it if they've got it right.''

It is now anybody's guess, she says, whether the heads of government will reach an agreement this weekend.

''It was a great journey into the unknown for all of us,'' she said. ''The draft is so complex that it's difficult to understand; yet I'm convinced that those who come to understand it may be forgiven for thinking that they have gone mad in the process.''