Does Haywards Heath count? There's a tunnel a few hundred yards to the south, isn't this particular tunnel the biggest barrier to four tracking the route between Balcombe tunnel junction and Brighton?
That's just a bridge with a building on it. If that counts then so does Ealing Broadway.
Very good point - I think it does! Not sure how I forgot that one from my list. Though some might argue that Balcombe Tunnel and the Ouse Valley Viaduct are the rather larger obstacles to quadruple track!
Kidbrooke is pretty close to a tunnel.
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Funny you should mention that just as I was posting, because the tunnel between Kidbrooke and Blackheath was similarly built because of a landowner not wanting the railway.