5:30pm (UK)

The Prince of Wales and Duchess of Cornwall took their royal tour of the United States to northern California.

They examined produce at a farmers' market and lunched with locals at an organic farm near San Francisco. Charles and Camilla will spend more than three days in the region.

The trip will shift the emphasis royal tour from the power centres of New York and Washington to remoter communities and issues close to the prince's heart -- organic agriculture and sustainable food production.

As well as the trip to a market and lunch on a nearby farm, the couple plan to visit a Berkeley school organic garden sponsored by chef Alice Waters.

The prince is a firm supporter of environmental causes, and runs an organic farm on his Highgrove estate in England.

Earlier the couple gazed over the devastated city of New Orleans in disbelief during a brief visit to witness first hand the damage caused by Hurricane Katrina.

They stood side by side atop a patched 20ft levee, shaking their heads as they took in the extent of the destruction. Splintered homes, chunks of concrete and overturned cars lay before them.

Charles and Camilla also met some of those whose lives were torn apart by the August 29 tragedy as well as rescue workers involved in the massive relief effort.

In New Orleans' historic French Quarter, Charles donned a string of Mardi Gras beads, given to him by a well-wisher, which he wore over his blue suit. Later, a woman presented Charles with a baseball hat emblazoned with the words Bring New Orleans Back.

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