Mersey Tunnel 

Large, oversized vagina that offers no sexual satisfaction

Look at that Mersey Tunnel. You could get lost in there.

Mersey Tunnel by ud40 February 23, 2005

Waving a chipolata in the Mersey Tunnel 

The sexual act, when performed with a woman of generous genital proportions. Or a man of diminutive proportions. Or both.

She was so loose I thought I'd have to strap a board across my arse to stop myself falling in. It was like waving a chipolata in the Mersey Tunnel.

Waving a chipolata in the Mersey Tunnel by Kojak October 28, 2003