Stupid question - I know! how do you open external meter cupboard?

[Bluebear]

Ok, so I'm a bit dim I admit!
Dh is away on business and we've just got a gas bill based on an estimate which is twice the usual amount. I need to read the meter but it's in one of those white cupboard things outside and I can't find a key - can I use pliers or something?
Don't make me admit my stupidity to dh please!

there's normally a little key, but yes i've used small pliers before

Thanks tutter - I used some pliers - scraped the lock a bit but got the reading. Have just done an 'irate but controlled' phone call to the power company and have had my bill recalculated