SEVERAL hundred mourners, including family members and Tanzanian officials, attended a memorial service on Saturday at Westminster Cathedral in London, for Tanzania’s former president Julius Nyerere. The widow of the African elder statesman, who died in London Thursday of leukemia, entered the ornate London cathedral behind her husband’s casket, which was draped in a Tanzanian flag. Nyerere, who led the former British colony to independence in 1961 and voluntarily relinquished the presidency in 1985, was widely revered both at home and abroad. He died at 77. His remains are to be buried in his birthplace in Tanzania next week.