1934 It sounds as if the pollarding is now not at it's best and disease/breaks etc. are likely to happen at any time. By all means have the tree taken out. As you have the railway, a screen is what you seem to need. You say there are three conifers in line with the acer, you could continue this line with the same type of conifers to form a hedge, cutting one side in the spring and one in the autumn. Let them grow and take out the tops when they reach the required height.

As long as the avenue of trees were not planted to mark some special occaision like the Queen's Coronation I would think that removing this 'ugly' tree is a reasonable idea. They were probably pollarded by the railway if there was any danger of them interfering with the trains.
While you are at it, why not remove the conifers and start with a clean sheet.

I'd be tempted to remove all of them and start with trees you would like to grow. or no trees at all just tall herbaceaous plants.

I'd also be tempted to remove all of them & plant with trees that give more interest through the year. i.e attractive bark, blossom in spring & autumn leaf colour or different evergreens. I've got a hedge of different colour Camellias, some flower in the autumn even.