What bdsl's comment means is this:
Suppose there was a way for "experts" (here or anywhere else) to predict when the pound would start depreciating against the euro, and that this method predicted that it would begin to do so tomorrow. What would the experts do with this information? They would start selling pounds today in order to get out of the market at the top. But this rush of selling activity would cause the value of the pound to fall (via the usual principle of supply and demand) today—a day earlier than forecast! This simple story illustrates the broader idea that a method for forecasting financial markets is self-defeating. As soon as anyone has information about the future direction of an asset price (be it currency exchange rates, stock prices, etc.), their buying or selling activity will, by itself, move the price in that direction. Thus, any information available to the public will be "built-in" to the market price you see quoted. Moreover, given the amounts of money at stake, large market actors have a huge incentive to act on new information very quickly so that information gets built into the price almost immediately.
This general principle—that it is impossible to use publicly available information to beat the market—is known as the efficient market hypothesis. So-called specialists who claim they can predict what the market will do usually fail to do better than a random guess. Such people usually earn their money from commissions or advisory fees rather than from profits on successful trades.