Written on stationery embossed "4 South End House / Montpelier Row / Twickenham / Middlesex."
De la Mare is referring to "Emblems of Experience" a volume of poetry Sassoon had privately printed in 1951. See MA 4706.4 for a more detailed discussion of the poems in the volume.
Sassoon's Introduction to which De la Mare refers is to "Sport from Within" by Frank Atherton Brown, published in 1952 with a foreword by Sassoon.
Commenting on Sassoon's new volume of poetry and a new volume of collected poems of Rupert Brooke; saying "There wasn't a single poem in your book which I didn't delight in sharing - really sharing - because every page is an admission into your solitude. And surely, all poems emanate from a solitude; though a good many appear to have a phantom audience sharply or vaguely in view - possibly one, possibly Posterity! Have you yourself any phantom audience actually present as you write? It is curious how a poem one reads again after an interval seems to have, without one being aware of it, passed through a change in one's memory. And that, oddly, if one cared for it, enchants one the more. Will this trouble in Egypt do you think have affected Geoffrey [Keynes] and Margaret in Khartum? He has contributed an introduction to an edition of Rupert Brooke's poems, and I feel pretty certain he thought me an absurdly prudish old prig because I could see no particular object in including a facetious poem by R.B. written for the amusement of the Ward during his last few days on the state of his bowels. Nothing fatal to our friendship. If only there were a good deal less of the suggestive and of what the comedians call the 'blue' about, and a sort of silly schoolboy conceit in a similar sort of thing, I should personally welcome much more of the old English coarse. What a subject, and how much I would like to go on. Do let me see your Introduction to the steeple-chasing book. And there was I that very week, I believe, absolutely stymied over a scrap of a review, (and that, I hope, my last). I am so ashamed after reading your list of the author's 'breakages' at having so far as I am aware all my bones in prime condition, that the only way out seems to be to make a mistake between the stairs and the window...I'm sure Gorge won't mind my sharing my love to you. Some day perhaps he'd come and have a look at Methuselah. I can hardly believe that the birds will so soon be singing again. My kitchen window sill is a sort of canteen for them, including even jackdaws. And how strangely fascinating it is to watch the gulls homing up the river every evening about sundown;" adding, above the date on the recto, a small note with an arrow which appears to be pointing to his last line on the verso which refers to his feeding the birds, "Surely not bread & butter!"