The Silver Maple Acer saccharinum is native to eastern and central North America from Newfoundland to Texas. It was introduced to Britain in 1725 and has been widely planted on city streets and parks. Its leaves are silvery underneath and it has bright red flowers in spring, before the leaves. All images and text taken from the book Field Guide to the Trees of Britain and Europe or the app Tree Guide UK
Silver Maple flowers in February

The tree comes into flower before the leaves, normally in March,  but this year in February following the mild winter. The tree in this photos has only female flowers.

Silver Maple female flower bud

A female flower bud that has just opened. Some trees have all female flowers, some all male and some have both. The flowers are wind-pollinated so have no petals. Each bud opens to reveal several flowers. A single female flower extends 2 long red stigmas to catch wind-blown pollen. They are connected to a single ovary which eventually forms a 2-winged fruit called a samara. The fruits hang down like a Sycamore. 

Silver Maple female flower buds

Female flower buds are located along or at the end of twigs.

Silver Maple female flower buds

When the female flower bud first opens the stigmas are white, then turn red.