Police spotting (junction watch)

That's completely wrong.

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Bus Lanes. Most bus lanes may be used by cyclists as indicated on signs.

Since there's a no cycling symbol on certain bus lane such as the bus lane on Bloomsbury Way, those without such symbol would suggested that we're allowed to ride on.

I'm not sure what the distinction is, should cyclists only be on bus lane if there's a sign/symbol for it, or if there's a marking stating that cyclists shouldn't be on it?