Last year's improbable Boston Marathon champions return to defend their titles.
European record holder Mo Farah is to run next year's London Marathon for the third time, organisers said on Tuesday.
Mo Farah, Britain's most successful distance runner, is set to compete at the London Marathon next year.
The four-time Olympic gold medalist over 5,000m and 10,000m is coming to the end of his first full year as a dedicated marathon runner, which saw him set a European record of 2:05:11 at the Chicago Marathon in October.
That result was an improvement on the 2:06:21 he had run in London six months previously -- at the time a British record.
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