Premiers from the world's leading economic powers will renew pressure on Russia to act over the crisis in Ukraine at a summit in Brussels.
Leaders of the G7 group of economic powers will also try to thrash out the outline of an agreement over tackling the threat from terror posed by the Syrian conflict.
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There will be patchy light rain across the UK, but sunny spells in the west.
The 650-feet long hole emerged after a water main burst near the 14th-century Ponte Vecchio bridge.