Commuters and comedians have been intrigued by posters that have been appearing on the London Underground. They are advertising Joe Lycett's upcoming shows at the SSE Wembley Arena on September 22 and 23 next year, but instead of featuring a picture of Lycett they feature a picture of comedian James Acaster.

This image here was tweeted by comedian Andy Smart, who asked: "What’s this about? Anyone else see something wrong with this poster?"

Steven Rankin wondered "my guess would be it's something to do with @joelycett got your back, maybe their doing a bit on false advertising?"

Kris Widakay pointed out that if it is an error it's a pricey one: "I cannot begin to describe how expensive those spots on the tube are. Assuming that is part of a London-wide campaign (a fair assumption methinks), that is a very costly mistake!"

David Smethurst joked that it looked like snooker legend Steve Davis. At least we assume he was joking.

Beccy Owen quipped: "Umm…that’s James A…! …all these hilarious, wiry white guys look the same…"

Others including comedians Mark Olver, Imran Yusuf and Bethany Black have also been amused by it. Comedian Lulu Popplewell has also noticed it. Popplewell asked on Twitter if someone at Lycett's management comany Chambers had slipped up: "Hey @joelycett can’t tell if this is a pranky goof or if someone at Chambers is getting fired?...i won’t sleep until I solve this glitch in the matrix please don’t leave me hanging. Is it a statement about false advertising? Is it like when sainsbury’s swaps out an item they’ve run out of? Is it a cock up? I must know. I have to know. I will not rest...The more I look the more I think it’s a definite prank but I want to know who masterminded it....But also I think it might be for JL’s got your back because he has form with the long con"

At the moment everyone is being tightlipped. Lycett and Chambers Management have not said anything and James Acaster is not currently on social media so if he is not involved he may not even know about it...

If you want to know the truth about the poster as soon as it's revealed follow me on Twitter @brucedes

Update - Joe Lycett has spoken...here.