[update] – Spoken to barclays and they confirmed this is an offical number it’s just not listed anywhere – helpful! – if in don’t call the regular customer services number.
Just got a call from person claiming to be Barclays, wanting to confirm some recent transactions on my card. I was suspicions so asked how I could proves she was from Barclays, maybe she could tell me the 1st line of address or year of birth, but all they could say was call back on 0800 015 8601. Which is similar to a Barclays number if you check the Barclays contact us page but it’s not actually listed. So be aware this in a ID theift SCAM!
See this thread too.