270 watts divided by 12.5 volts = 21.6 amps. Fully charged, one would think that 110 amp-hours divide by 21.6 would give you o.509 hours. But there ain't no such thing as 'fully charged' outside a laboratory - 95% is probably the best you'll get. And running a leisure down to flat is bad news - as is anything below 40% or 25% depending on which 'knowledgeable expert' is consulted.
Add in the thought that leisure batteries don't like to deliver power very fast - taking 10 hours to discharge is ' fast'. Above this rate, the volts drop rapidly, and more Amps are needed to give you 270 Watts.
Therefore the answer to your question is 'About a quarter of an hour' A longer answer says 'About a quarter of an hour for a couple of dozen times only'.