Daud, AAbogun, S.2021-06-072021-06-0720175. Daud, A. & Abogun, S. (2017): Testing the Validity of the Weak form Market Efficiency in the UK Stock Exchange: Evidence from London Stock Market. Ilorin Journal of Finance. 1(1); 65-81, Published by Department of Finance, University of Ilorinhttps://uilspace.unilorin.edu.ng/handle/20.500.12484/6030The mixed results from a wide range of research and a new concern raised by Moore (2006) that United Kingdom market participants did not display a rational behavior in the lead up to and aftermath of the British referendum to leave the European union motivated a new research into market efficiency of the London stock exchange using larger sample size hat reflects more recent trading. Therefore, this research work examined whether the London stock exchange is weak form efficient using the random walk theory. Three objectives were formulated based on three different statistical methods of testing for randomness in price series. The log returns of Financial Times Stock Exchange 250 share index between 1986 to 2016 were examined using serial correction test, variance ratio test and unit root test. The three statistical tests agree that the randomness of successive stock prices do not hold in the London stock exchange. Therefore, the result of this research work suggests that London stock exchange is not informationally efficient in the weak form. This implies that prices of stocks listed on the London stock exchange may not be a true reflection of asset value and opportunities exist for technical and fundamental analysts to study stock trend and predict future prices. Based on the conclusion, the study recommended that: firms should ensure good information management and a very cautious investment strategy that put into consideration the possibility of overreaction from investors.enEfficient Market HypothesisRandom Walk TheoryPrice SeriesWeak FormStock ExchangeArticle