Einstein, eccentric genius, smoked butts picked up off street

"An insight into the eccentric life of Albert Einstein has been provided in a letter written by his favourite grandson.

Bernhard Caesar Einstein, 75, who has never previously spoken about his relative, has recounted a string of anecdotes about the often bizarre life of the 20th century's greatest scientist.

At one point, the younger Mr Einstein recalled, his grandfather resorted to collecting cigarette butts from the streets to circumvent his doctor's effort to stop him from smoking.

In the letter, filed away and forgotten for seven years, the grandson recalled receiving a baffling three-hour lecture from Einstein on the mathematical properties of soap bubbles. He was aged eight at the time. The lecture was delivered while the two were alone on a becalmed sailing boat. Einstein, his grandson recalled, deliberately went out sailing when there was no wind because he felt it was more challenging.

"While at Knollwood [in America] my grandfather and I frequently went sailing together," Mr Einstein told Françoise Wolff, a Belgian documentary maker, in the letter.

"He usually said very little to me during those outings but on one particular afternoon, one on which there was practically no wind, he became talkative.

"He liked the calm and claimed that calm was the highest challenge to the sailor. We went no further than about a kilometre in the three hours we were out. My grandfather talked continuously about soap bubbles, and of course in mathematical terms. I did not understand a word of what he said."

Ms Wolff asked Mr Einstein to take part in her 1998 documentary because he was one of the few people with memories of the German-born genius, whose Theory of Relativity turned physics upside down and led to the development of nuclear power.

Because of illness, however, his contribution arrived too late to be used. His letter was published for the first time last week on the website of a Belgian newspaper, Le Soir, ahead of a repeat showing of the documentary.

Mr Einstein, himself a physicist who divides his time between Switzerland and America, confesses touchingly to "loving his grandfather as soon as he saw him". He also remembered his sterner side: he was a steadfast opponent of his young relative's passion for angling for sport.

"Grandfather would only allow me to go fishing if I ate all the fish I caught, so I caught one fish early in the morning and ate it for breakfast."

The scientist befriended the humble as well as the great, his grandson wrote. If he wasn't writing to President Roosevelt about the approaching Second World War he could be found playing chamber music with the local greengrocer.

His two prized possessions were his violin and his pipe, and his reliance on the latter "bordered on dependency". When forbidden from smoking by his doctor he would sneak out and collect cigarette "dog-ends" from the street to fill his pipe. "It's a rather sad anecdote," said Peter Smith, the author of the biography Einstein.

While known for getting along well with children, Einstein had a strained relationship with his two sons. He was disappointed in his grandson, too, when he discovered that he was not a brilliant physicist.

"I was 25 then," Mr Einstein recalled. "He had given me $5,000 for my studies in Zurich and later gave me money for furniture. That afternoon he talked to me for the first time ever about physics. He asked me what I knew about energy, but he dropped the question immediately when he realised that I could not discuss the subject on his terms.

"That was the last time I saw him.'"