Citigo Elegance ASG.

For some time I have had an intermittent problem with the ignition key jamming in the sense that it is in position, but will not turn. Moving the gear selector into various positions appears, eventually, to release whatever is holding the key from moving. I raised this when the car was MOTed, 3 years old, in September, & was told it had been solved, but it appears not. I suspect it is the gearbox rather than the ignition lock, but who knows? An ideas?

Have you tried pulling the steering wheel side to side whilst turning the key? 

nbJubilee, No I have not tried that, but will do so next time not happens. By side to side, you mean turning the wheel, rather than literally side to side? Thanks. 

Yes, turn the wheel or jiggle as you twist the key. Only do this if the steering lock has engaged preventing normal key turn.