The Himalayas

I met another dog walker where the Offa's Dyke Path goes through a field by the riverbank. On each side of the path, there are purple flowers higher than a man's head.
"Any idea what those are?" the man asked.
"Himalayan balsam," I said.
"Are they local?"
They're Himalayan," I said. "They drown out the local plants. The Wildlife Trusts are quite worried about them."
"Himalayan? I've been invited to go to the Himalayas," he said, and went on to tell me that a doctor who lives near him has asked him to take part in medical experiments at Mount Everest base camp! "Trouble is, you have to be able to walk so many miles with a backpack in the UK," he said, "and I find it enough to walk down to Shepherds these days."