When can you cut your grass after the winter depends on the weather, your soil and how long your lawn is. There is no simple answer for British and Irish gardeners.
If winter has been particularly mild and you live in Cornwall or the South West of Ireland you may have been able to cut your lawn all winter. I live in Cork and normally my last cut is in late November. The later your last cut, the shorter your grass will be in spring.
Your lawn needs to be dry enough to run a mower over it. Even if you use a hover mower you have to walk on the grass. If your lawn is sodden and you sink into the ground then it is best to stay off it. Electric lawn mowers will not cut wet grass at all. Petrol mowers manage better. It is best to wait until early afternoon, to let the grass dry out a bit from the overnight dew.
If your garden is blessed with clay soil then you might have to wait an extra week to let the ground dry out a bit after winter and spring rain.
If your lawn is a bowling green then you will need to cut it in February to keep it growing healthily. Make the first cut half an inch longer than you normally would. In warmer parts of Britain and Ireland you will need to cut your grass as soon as it starts growing again in late February.
Make your first cut of the lawn about 1in longer than usual to encourage its spring regrowth.