Any question answered...

We're riding out to Brands Hatch tomorrow for a wedding reception and google pedometer's suggested route puts us through the Blackwall tunnel. I've read on here plenty of times that it's dangerous, but I've never used it myself. Is it really so bad that we should give the tunnel a miss?

Blackwall Tunnel is out of bounds. Plus there are regular closures due to the construction works.
Rotherhive Tunnel is very scary - especially on a hot day, due to the high level of pollution. Forget about it if you have asthma.

Try Woolwich ferry or Tower Bridge.