Tories expected to target voters with letters signed by Boris Johnson

Tens of thousands of letters signed by former prime minister expected to be delivered this week

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The Conservatives will turn to Boris Johnson in an attempt to boost their faltering election campaign, according to reports.

Tens of thousands of letters signed by the former prime minister are expected to be delivered later this week in the closest campaign engagement yet by Johnson, whose involvement so far has been limited to endorsing individual Tory MPs.