LONDON, England - Cold, cold, cold.  That was Downing street when I arrived before dawn this morning. I'd dressed for it, no big deal. Waiting outside the British prime minister's house - Number 10 - has a reputation for being one of the coldest places if not in the whole south of England, then certainly London.  Today was going to be no different.

U.S. Secretary of State Hillary Clinton and British Foreign Minister David Miliband enjoy the sunshine outside Number 10.

By about 7.30 a.m., the sun had been up for about an hour and the blue sky hinted that Barack Obama's first day in Britain in over a decade was going to be a nice one. Lucky him. Some American tourists come here for week and will remember for a lifetime unrelenting grey skies and rain.

As 8 a.m. and the U.S. president's expected arrival approached, we were getting agitated, which was good – any movement tends to generate heat. Most of those gathered around me had never seen Barack Obama in the flesh before.  For a bunch of hard-bitten hacks you could say the mood was one of muted excitement.

Then something nice, really nice happened.  The sun rounded the corner of Downing Street.  It runs north-south, and from the southern end the sun pushed out shining in full warmth, inducing splendor from between the spokes of the giant London Eye. 

The huge wheel stands on the far side of the River Thames. For the cost of a few pints of beer, it slowly carries tourists high above the rooftops for a spectacular view of this ancient city.

The sun's rays splattered us, filling us with hope we may yet heat up. Unfortunately it also that meant we had to squint really hard to see if the presidential limo was pulling in to the street.

So it was, as Barack and Michelle Obama finally arrived at the door of number 10 and clambered out of the "Beast" - their ultra-armored truck/car - to greet Gordon and Sarah Brown, the street was bathed in bright sunshine. Well, all apart from the tiny spot where the foursome smiled warmly at each other and almost equally affectionately toward the cameras.

That's when I noticed there is a special inner warmth that spreads with the feeling that you're covering something that has the potential to be a good news story. Despite the talk of divisions we were witnesses to the beginning of a week that could yet prove to be a defining moment in history.

Then they were gone, whisked indoors so the serious stuff could begin. But before the big polished portal of number 10 could fully pull closed behind them, there was the sound of loud and hearty clapping from the corridors of power within. The world's most popular politician it seems was brightening and warming the lives of Mr. Brown's staff.

Within minutes though, somewhat disappointingly, as quickly as the sun had come, it was gone, continuing its westward path beyond Downing Street's narrow southern entrance.

For a moment we'd had the sun and the stars, now we had neither, which goes part of the way to explain why my fingers were almost too cold to take legible notes during their press conference two hours later.