Nicholas Jacobs, 44, was remanded in custody until Friday by Westminster Magistrates' Court after being charged with the murder of Pc Keith Blakelock.
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Council workers uncovered the AK-74 concealed in the undergrowth.
The thief, who used a walking stick, was helped by a man who disabled the lock before pushing the woman away.
More than 40,000 new property millionaires have been created across Britain this year so far amid rising house prices.