“That’s a load of cobblers.” I’m not sure where I heard this expression recently, but it’s common and I thought that it probably was rhyming slang (slang in which a word is replaced by a phrase which rhymes with it). I checked it in my Cassell’s rhyming slang, by Jonathon Green:

cobbler’s (also cobblers, cobblers’ awls, cobbler’s stalls)

[1930s+] 1 the testicles. 2 rubbish, nonsense, esp. as an exclamation cobblers! [cobbler’s awls = balls]

An awl is a pointed tool for making holes, as in wood or leather, and is an essential tool for a shoemaker (or cobbler). According to cockneyrhymingslang.co.uk, balls can also be Niagara Falls (I got booted in the Niagaras).
On the same page, I spotted a couple of expressions linked to Brighton, my home town. So, here is a little challenge for the weekend: what do Brighton pier and Brighton rock mean in rhyming slang? Suggestions in the comments box, the first person to find the answers will win my undying admiration.